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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No.          )

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AON CORPORATION

NOTICE OF 2011 ANNUAL MEETING OF STOCKHOLDERS

To the Holders of Common Stock of Aon Corporation:

        The 2011 Annual Meeting of Stockholders of Aon Corporation will be held on Friday, May 20, 2011, at 8:30 A.M (local time), at the Indiana Room, Aon Center, 200 East Randolph Street, Chicago, Illinois 60601, for the following purposes:

1.

To elect the sixteen nominees named in the attached proxy statement to serve as Directors until our 2012 Annual Meeting of Stockholders. Our Board of Directors unanimously recommends that you vote "FOR" the election of all sixteen nominees.



2.

To ratify the appointment of Ernst & Young LLP as our independent registered public accounting firm for the year 2011. Our Board of Directors unanimously recommends that you vote "FOR" the ratification of the appointment of Ernst & Young LLP as our independent registered public accounting firm for the year 2011.



3.

To hold an advisory vote on executive compensation. Our Board of Directors unanimously recommends that you vote "FOR" advisory approval of the compensation of Aon's named executive officers.



4.

To hold an advisory vote on the frequency of holding an advisory vote on executive compensation. Our Board of Directors unanimously recommends that you vote "FOR" conducting an advisory vote on the compensation of our named executive officers every year.



5.

To approve the Aon Corporation 2011 Incentive Plan. Our Board of Directors unanimously recommends that you vote "FOR" the approval of the Aon Corporation 2011 Incentive Plan.



6.

To approve the Aon Corporation 2011 Employee Stock Purchase Plan. Our Board of Directors unanimously recommends that you vote "FOR" the approval of the Aon Corporation 2011 Employee Stock Purchase Plan.



7.

To transact such other business as may properly come before the 2011 Annual Meeting of Stockholders or any adjournment or postponement thereof.

        Only holders of common stock at the close of business on March 30, 2011 are entitled to notice of and to vote at the 2011 Annual Meeting of Stockholders and any adjournment or postponement thereof. A list of the stockholders entitled to vote at the 2011 Annual Meeting will be available for inspection, for any purpose germane to the 2011 Annual Meeting, both at the 2011 Annual Meeting and during normal business hours at our corporate offices for ten days prior to the 2011 Annual Meeting.

        This year, we will continue to use the notice and access rules adopted by the Securities and Exchange Commission to provide our stockholders access to our proxy materials through the Internet. As a result, we will mail a Notice of Internet Availability of Proxy Materials to most of our stockholders on or before April 8, 2011, that provides instructions for accessing and reviewing the proxy materials and voting electronically using the Internet. We will also deliver printed versions of the proxy materials to certain of our stockholders, including those who have previously requested paper copies of the proxy materials. On the date of mailing of the Notice of Internet Availability of Proxy Materials, all stockholders will be able to access the proxy materials on a website referred to and at the URL address

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included in the Notice of Internet Availability of Proxy Materials and in the proxy statement. These proxy materials will be available free of charge.

Chicago, Illinois
April 8, 2011

        Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting of Stockholders to be held on May 20, 2011. Our Proxy Statement for the 2011 Annual Meeting of Stockholders and the Annual Report to Stockholders for the fiscal year ended December 31, 2010 are available at http://www.envisionreports.com/AON if you are a stockholder of record, and http://www.edocumentview.com/AON if you are a beneficial owner.

        Your vote is important. Whether or not you plan to attend the 2011 Annual Meeting of Stockholders, please vote as promptly as possible by telephone, through the Internet or by requesting a paper proxy card to complete, sign and return by mail.

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Aon Corporation
200 East Randolph Street
Chicago, Illinois 60601

PROXY STATEMENT
ANNUAL MEETING OF STOCKHOLDERS – MAY 20, 2011

INFORMATION ABOUT THIS PROXY STATEMENT AND THE 2011 ANNUAL MEETING

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        The Board of Directors (the "Board") of Aon Corporation ("Aon") is soliciting your proxy to vote at the 2011 Annual Meeting of Stockholders (the "Annual Meeting") to be held at the Indiana Room, Aon Center, 200 East Randolph Street, Chicago Illinois 60601, at 8:30 a.m. (local time), on Friday, May 20, 2011, and at any adjournment or postponement thereof.

        As permitted by the rules of the Securities and Exchange Commission (the "SEC"), we are making our proxy materials, including the Notice of 2011 Annual Meeting of Stockholders, this proxy statement and the accompanying proxy card, and our Annual Report to Stockholders (collectively, the "proxy materials"), available to stockholders electronically via the Internet on April 8, 2011. On the same date, we began mailing to most of our stockholders a Notice of Internet Availability of Proxy Materials (the "Notice of Internet Availability") containing instructions on how to access our proxy materials and vote online. We are also delivering printed versions of the proxy materials to certain of our stockholders, including those who have previously requested paper copies of the proxy materials. If you received a Notice of Internet Availability, you will not receive a printed copy of the proxy materials unless you have previously made a permanent election to receive these materials in hard copy. Instead, the Notice of Internet Availability instructs you as to how you may access and review all of the important information contained in the proxy materials. The Notice of Internet Availability also instructs you as to how you may submit your proxy on the Internet. If you received a Notice of Internet Availability by mail and would like to receive a printed copy of our proxy materials, you should follow the instructions for requesting such materials included in the Notice of Internet Availability.

        Aon's Annual Report to Stockholders, which contains Aon's Annual Report on Form 10-K, including consolidated financial statements for the year ended December 31, 2010 but excluding exhibits, accompanies this proxy statement. Requests for copies of exhibits to Aon's Annual Report on Form 10-K should be submitted to the Office of the Corporate Secretary, Aon Corporation, 200 East Randolph Street, Chicago, Illinois 60601. Exhibits will be furnished upon payment of a nominal fee (which fee will be limited to the expenses we incur in providing you with the requested exhibits). Aon's Annual Report on Form 10-K, including exhibits, are also available free of charge through our website (http://www.aon.com).

         Why did I receive these proxy materials?

        We have made these proxy materials available to you on the Internet or have delivered printed versions of the proxy materials to you by mail, in connection with the solicitation of proxies for use at the Annual Meeting, and at any adjournment or postponement thereof.

        The Notice of Internet Availability was first mailed on or before April 8, 2011 to stockholders of record as of March 30, 2011, which we refer to as the "record date."

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         What matters will be presented for consideration at the Annual Meeting?

        Action will be taken at the Annual Meeting with respect to the following proposals:

1.

The election of the sixteen nominees named in this proxy statement to serve as Directors until our 2012 Annual Meeting of Stockholders.



2.

The ratification of the appointment of Ernst & Young LLP ("E&Y") as our independent registered public accounting firm for the year 2011.



3.

An advisory vote on executive compensation.



4.

An advisory vote on the frequency of holding an advisory vote on executive compensation.



5.

The approval of the Aon Corporation 2011 Incentive Plan.



6.

The approval of the Aon Corporation 2011 Employee Stock Purchase Plan.

         Will any other matters be decided at the Annual Meeting?

        At the date of this proxy statement, we do not know of any other matters to be raised at the Annual Meeting other than those described in this proxy statement. If any other matters are properly presented at the Annual Meeting for consideration, the individuals named in the proxy card will vote on such matters in their discretion.

         Who is entitled to vote at the Annual Meeting?

        Holders of our common stock, par value $1.00 per share (the "Common Stock") as of the close of business on March 30, 2011, are entitled to vote at the Annual Meeting. As of that date, there were 330,505,341 shares of Common Stock outstanding and entitled to vote. Each share of Common Stock is entitled to one vote on each matter properly brought before the Annual Meeting.

         What is the difference between holding shares of Common Stock as a stockholder of record and as a beneficial owner?

        If your shares of Common Stock are registered directly in your name with Aon's transfer agent, Computershare Trust Company, N.A., you are considered, with respect to those shares of Common Stock, the stockholder of record, and these proxy materials are being made available or sent directly to you by Aon.

        If your shares of Common Stock are held in a stock brokerage account or by a broker, bank or other nominee, you are considered the beneficial owner of shares held in street name, and these proxy materials are being made available or forwarded to you by your broker, bank or other nominee who is considered, with respect to those shares, the stockholder of record. As the beneficial owner, you have the right to direct your broker, bank or other nominee on how to vote your shares of Common Stock by following the instructions for voting on the proxy card or Notice of Internet Availability.

         How do I vote?

        If you are a stockholder of record, you may vote using any of the following methods:

•

By telephone using the toll-free telephone number shown on the proxy card;



•

Through the Internet as instructed on the proxy card or the Notice of Internet Availability;



•

If you received proxy materials by mail or if you request a paper proxy card by telephone or through the Internet, you may elect to vote by mail by completing and signing the proxy card and returning it in the prepaid envelope provided; or

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•

By written ballot at the Annual Meeting.

        Telephone and Internet voting facilities for stockholders of record will be available 24 hours a day. If you vote by telephone or through the Internet, your vote must be received by 11:59 p.m., Eastern Time, on Thursday, May 19, 2011, the day before the Annual Meeting. If you properly cast your vote by telephone, through the Internet or by executing and returning a paper proxy card, and your vote is not subsequently revoked, your Common Stock will be voted in accordance with your instructions. If you execute and return a proxy card but do not give instructions, your proxy will be voted as follows: FOR the election of all nominees for Director named in this proxy statement; FOR the ratification of the appointment of E&Y as our independent registered public accounting firm for the year 2011; FOR advisory approval of the compensation of our named executive officers; FOR conducting an advisory vote on the compensation of our named executive officers every year; FOR the approval of the Aon Corporation 2011 Incentive Plan; and FOR the approval of the Aon Corporation 2011 Employee Stock Purchase Plan, and otherwise in accordance with the judgment of the person or persons voting the proxy on any other matter properly brought before the Annual Meeting.

        If you are a beneficial owner, you should follow the voting directions provided by your broker, bank or other nominee. You may submit voting instructions by telephone or through the Internet to your broker, bank or other nominee, or request and return a paper proxy card. If you hold shares through the Aon Savings Plan, the plan trustees will vote according to the instructions received from you provided your voting instruction is received by 11:59 p.m., Eastern Time, on Wednesday, May 18, 2011.

        We will distribute written ballots to anyone who wants to vote in person at the Annual Meeting. If you are a beneficial owner, you must obtain a legal proxy from your broker, bank or other nominee and present it to the inspectors of election with your ballot to be able to vote at the Annual Meeting.

         What should I do if I receive more than one notice of internet availability of proxy materials or proxy card?

        If you own shares of Common Stock directly in your name as a registered holder and other shares of Common Stock as a beneficial owner through a broker, bank or other nominee, or if you own shares of Common Stock through more than one broker, bank or other nominee, you may receive multiple Notices of Internet Availability or, if you request proxy materials to be delivered to you by mail, multiple proxy cards. It is necessary for you to vote, sign and return all of the proxy cards or follow the instructions for any alternative voting procedure on each of the Notices of Internet Availability you receive in order to vote all of the shares you own. If you request proxy materials to be delivered to you by mail, each proxy card you receive will come with its own prepaid return envelope. If you vote by mail make sure you return each proxy card in the return envelope which accompanied that proxy card.

         How is a quorum determined?

        The presence of the holders of a majority of the shares of Common Stock issued and outstanding and entitled to vote at the Annual Meeting, in person or represented by proxy, is necessary to constitute a quorum. Abstentions and broker non-votes will be counted as present and entitled to vote for purposes of determining a quorum at the Annual Meeting.

         What is a broker non-vote?

        If you own your shares of Common Stock through a broker, bank or other nominee, and do not provide the organization that holds your shares of Common Stock with specific voting instructions, the bank, broker or other nominee may generally vote your shares of Common Stock in its discretion on certain routine matters. With respect to certain non-routine matters, the broker, bank or other nominee

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is not permitted to vote your shares of Common Stock for you. A broker non-vote occurs when a broker, bank or other nominee holding shares of Common Stock on your behalf, does not vote on a particular proposal because it has not received voting instructions from you and does not have discretionary voting power with respect to that proposal. If the broker, bank or other nominee that holds your shares of Common Stock does not receive voting instructions from you on how to vote your shares of Common Stock on a non-routine matter, it will inform the inspector of election that it does not have the authority to vote on that matter with respect to your shares of Common Stock.

         What proposals are considered "routine" or "non-routine"?

        The ratification of the appointment of E&Y as Aon's independent registered public accounting firm for 2011 (Proposal 2) is considered a routine matter under the rules of the New York Stock Exchange (the "NYSE"). A broker, bank or other nominee may generally vote on routine matters, and therefore no broker non-votes are expected to occur in connection with Proposal 2.

        The election of Directors (Proposal 1), the advisory vote on executive compensation (Proposal 3), the advisory vote on the frequency of holding an advisory vote on executive compensation (Proposal 4), the approval of the Aon Corporation 2011 Incentive Plan (Proposal 5) and the approval of the Aon Corporation 2011 Employee Stock Purchase Plan (Proposal 6) are matters considered non-routine under the rules of the NYSE. A broker, bank or other nominee may not vote on these non-routine matters without specific voting instructions from the beneficial owner. As a result, there may be broker non-votes with respect to Proposals 1, 3, 4, 5 and 6.

         What are the voting requirements to elect Directors and approve each of the proposals?

        The election of each of the sixteen nominees for Director named in this proxy statement will be decided by a majority of the votes cast with respect to such Director, which means that the number of votes cast for a nominee for Director must exceed the number of votes cast against that nominee for Director. Abstentions and broker non-votes will not be counted as a vote either for or against a nominee for Director. If the number of votes cast against a nominee exceed the number of votes cast for a nominee, the nominee must immediately offer to tender his or resignation, and the Board, through a process managed by the Governance/Nominating Committee, will determine whether to accept or reject the resignation, or take other action.

        The ratification of the appointment of E&Y as Aon's independent registered public accounting firm, the advisory vote on executive compensation, the approval of the Aon Corporation 2011 Incentive Plan, and the approval of the Aon Corporation 2011 Employee Stock Purchase Plan each requires the affirmative vote of the holders of a majority of the shares of Common Stock present in person or represented by proxy and entitled to vote at the Annual Meeting. The advisory vote on the frequency of holding an advisory vote on executive compensation will be determined by a plurality of the votes cast. For the ratification of the appointment of E&Y as Aon's independent registered public accounting firm, the advisory vote on executive compensation, the approval of the Aon Corporation 2011 Incentive Plan, and the approval of the Aon Corporation 2011 Employee Stock Purchase Plan, a stockholder who submits a properly executed ballot or proxy is considered present and entitled to vote, so an abstention will have the effect of a vote against the applicable proposal.

         Can I change my vote?

        If you are a stockholder of record, you can change your vote or revoke your proxy at any time before the Annual Meeting by:

•

Entering a later-dated vote by telephone or through the Internet;

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Delivering a valid, later-dated proxy card;



•

Sending written notice to the Office of the Corporate Secretary of Aon; or



•

Voting by ballot in person at the Annual Meeting.

        If you are a beneficial owner of shares of Common Stock, you may submit new voting instructions by contacting your broker, bank or other nominee. You may also vote in person at the Annual Meeting if you obtain a legal proxy as described above under "How do I vote?"

        All shares of Common Stock that have been properly voted and not revoked will be voted at the Annual Meeting. Attending the Annual Meeting without taking further action will not automatically revoke your prior telephone or Internet vote or your proxy.

         Will the Annual Meeting be webcast?

        You may listen to the Annual Meeting on the World Wide Web by logging on to our website at www.aon.com and following the on-screen instructions. We have included our website address in this proxy statement for reference purposes only. The information contained on our website is not incorporated by reference into this proxy statement.

         Who can attend the Annual Meeting?

        Stockholders as of the close of business on March 30, 2011, which is the record date for voting, may attend the Annual Meeting.

         What do I need to do to attend the Annual Meeting?

        If you are a stockholder of record, you do not need to take any additional action in order to attend the Annual Meeting. If you are a beneficial owner of shares of Common Stock and would like to attend the Annual Meeting, you will need to bring an account statement or other acceptable evidence of ownership of your Common Stock as of the close of business on March 30, 2011, which is the record date for voting. Alternatively, you may contact the broker, bank or other nominee in whose name your Common Stock is registered and obtain a proxy to bring to the Annual Meeting.

         Who will pay the costs of this proxy solicitation?

        We will pay the expenses of the preparation of proxy materials and the solicitation of proxies for the Annual Meeting. In addition to the solicitation of proxies by mail, solicitation may be made on our behalf by certain Directors, officers or employees of Aon and our subsidiaries telephonically, electronically or by other means of communication, and by Georgeson Shareholder Communications Inc., whom we have hired to assist in the solicitation and distribution of proxies. Directors, officers and employees of Aon and our subsidiaries will receive no additional compensation for such solicitation. Georgeson will receive a fee of $10,000 for its services. We will also reimburse banks, brokers and other nominees for reasonable expenses incurred by them in forwarding proxy materials to beneficial owners.

         Who will count the vote?

        Representatives of our transfer agent, Computershare Trust Company, N.A., will count the vote and serve as inspectors of election.

         Where can I find the voting results of the Annual Meeting?

        The preliminary voting results will be announced at the Annual Meeting. The final voting results will be tallied by the inspector of election and disclosed in a Current Report on Form 8-K, which Aon is required to file with the SEC within four business days following the Annual Meeting.

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PRINCIPAL HOLDERS OF VOTING SECURITIES

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        As of February 28, 2011, the beneficial owners of 5% or more of our Common Stock entitled to vote at the Annual Meeting and known to us were:

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PROPOSAL 1—ELECTION OF DIRECTORS

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        Sixteen Directors are to be elected at the Annual Meeting. All of the current members of our Board of Directors are standing for election. With respect to Mr. Case, his employment agreement provides that he will be nominated for election as a Director at each annual meeting of stockholders during the period of his employment. With respect to Ms. Francis and Mr. Green, the Agreement and Plan of Merger dated as of July 11, 2010 among Aon, Hewitt Associates, Inc. ("Hewitt"), and two subsidiaries of Aon related to the merger of Hewitt with a subsidiary of Aon, provides that each of Ms. Francis and Mr. Green will be nominated for re-election to our Board of Directors at the Annual Meeting. The term of each Director expires at the next Annual Meeting of Stockholders, and each Director will continue in office until the election and qualification of his or her respective successor or until his or her earlier death, removal or resignation. The Board consists of a number of Directors as is fixed from time to time by resolution adopted by the Board as provided in our bylaws. Consistent with the terms of Aon's certificate of incorporation, the Board currently is authorized to have up to twenty-one members.

        All nominees are currently Directors of Aon. All nominees for Director have consented to be named and have agreed to serve as Directors if elected. The Governance/Nominating Committee recommended to the full Board that each Director be nominated to serve for an additional term.

        Each of the sixteen Directors will be elected by the vote of a majority of the votes cast with respect to such Director, which means that the number of votes cast for a nominee for Director must exceed the number of votes cast against that nominee for Director. A stockholder may: (i) vote for the election of a nominee for Director; (ii) vote against the election of a nominee for Director; or (iii) abstain from voting for a nominee for Director.

        Unless a proxy directs to the contrary, it is intended that the proxies will be voted FOR the election of the sixteen nominees for Director named on the following pages, to hold office until the next Annual Meeting of Stockholders or until their respective successors are duly elected and qualified. We have no reason to believe that any of the nominees will not be available to serve as a Director. However, if any of them should become unavailable to serve for any reason, the proxies will be voted for such substitute nominees as may be designated by the Board.

        Aon values a number of attributes and criteria when identifying candidates to serve as a Director, including professional background, expertise, reputation for integrity, business, financial and management experience, leadership capabilities and diversity. In addition to the specific experience and qualifications set forth below, we believe all of the nominees are individuals with a reputation for integrity, demonstrate strong leadership capabilities and are able to work collaboratively to make contributions to the Board and management.

        Set forth on the following pages is biographical and other background information concerning each nominee for election as a Director. This information includes each nominee's principal occupation as well as a discussion of the specific experience, qualifications, attributes, and skills of each nominee that led to the Board's conclusion that each nominee should serve as a Director. In addition, set forth below is the period during which each nominee has served as a Director of Aon, including service as a Director of Ryan Insurance Group, Inc. ("Ryan Group"), which merged with Aon in 1982. The information presented below has been confirmed by each nominee for purposes of its inclusion in this proxy statement. Ages shown for all Directors are as of December 31, 2010.

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        OUR BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT YOU VOTE "FOR" THE ELECTION OF ALL NOMINEES.

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SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

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        The following table sets forth the number of shares of Common Stock beneficially owned as of February 28, 2011 by each Director and nominee, by each of the named executive officers of Aon as set forth in the Summary Compensation Table for Fiscal Years 2010, 2009 and 2008 in this proxy statement, and by all Directors, nominees and executive officers of Aon as a group. As used in this proxy statement, "beneficially owned" means a person has, or may have within 60 days, the sole or shared power to vote or direct the voting of a security and/or the sole or shared investment power with respect to a security (i.e., the power to dispose or direct the disposition of a security). Therefore, the table does not include the "phantom stock" shares held by or attributable to any individual under our benefit plans. Information with respect to shares attributable to Aon's Directors under various deferral accounts is set forth in the section captioned "2010 Director Compensation."

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CORPORATE GOVERNANCE

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        The Board has adopted Governance Guidelines (the "Governance Guidelines") that provide the framework for the governance of Aon together with the Committee charters, the Code of Business Conduct, which sets forth standards of conduct for employees, officers and Directors, and the Code of Ethics for Senior Financial Officers. The Board provides oversight of Aon's overall performance, strategic direction, and executive management team performance. The Board also approves major initiatives and transactions and advises on key financial and business matters. The Board is kept apprised of Aon's progress on a regular basis through Board and Committee meetings, discussions with management, operating and financial reports provided by the Chief Executive Officer and Chief Financial Officer, and other material distributed to the Directors throughout the year.

        The Governance Guidelines require that Aon have a majority of Directors who meet the categorical independence standards adopted by the Board, which must meet or exceed the independence requirements of the NYSE corporate governance standards. The Governance Guidelines further provide that each of the Audit, Governance/Nominating and Organization and Compensation Committees will be composed entirely of independent Directors. The principal responsibilities of each Committee are described in this proxy statement in the section captioned "Board of Directors and Committees."

Director Independence

        In accordance with the rules of the NYSE, the Board has adopted categorical independence standards, which either meet or exceed the independence requirements of the NYSE corporate governance standards, to provide assistance in the determination of director independence. The categorical standards are set forth below and provide that a Director of Aon will not qualify as an independent Director if:

(i)

The Director is, or has been within the last three years, an employee of Aon, or an immediate family member of the Director is, or has been within the last three years, an executive officer, of Aon;



(ii)

The Director has received, or has an immediate family member who has received, during any twelve-month period within the last three years, more than $120,000 in direct compensation from Aon, other than director and committee fees and pension or other forms of deferred compensation for prior service (provided such compensation is not contingent in any way on continued service);



(iii)

(A) The Director is a current partner or employee of a firm that is Aon's internal or external auditor; (B) the Director has an immediate family member who is a current partner of such a firm; (C) the Director has an immediate family member who is a current employee of such a firm and personally works on Aon's audit; or (D) the Director or an immediate family member was within the last three years a partner or employee of such a firm and personally worked on Aon's audit within that time;



(iv)

The Director or an immediate family member is, or has been within the last three years, employed as an executive officer of another company where any of Aon's present executive officers at the same time serves or served on that company's compensation committee;



(v)

The Director is a current employee, or an immediate family member is a current executive officer, of a company that has made payments to, or received payments from, Aon for

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property or services in an amount which, in any of the last three fiscal years, exceeded the greater of $1 million or 2% of such other company's consolidated gross revenues; or

(vi)

The Director, or the spouse of a Director, serves as an executive officer of a charitable organization to which Aon's charitable contributions in the last fiscal year, excluding those made under Aon's matching gift program, exceeded the greater of $1 million or two percent (2%) of such organization's consolidated gross revenues.

        For purposes of the categorical standards, "immediate family member" is defined to include a Director's spouse, parents, children, siblings, mothers and fathers-in-law, sons and daughters-in-law, brothers and sisters-in-law, and anyone (other than domestic employees) who shares the Director's home.

        In connection with the determination of director independence, the Governance/Nominating Committee reviewed the categorical standards adopted by the Board together with other applicable legal requirements and the rules of the NYSE. The Governance/Nominating Committee also reviewed information compiled from the responses to questionnaires completed by each of Aon's Directors, information derived from Aon's corporate and financial records, information available from public records, and information received from other relevant parties. Following this review, the Governance/Nominating Committee delivered a report to the full Board of Directors, and the Board made its determination of director independence.

        As a result of this review, the Board affirmatively determined that each of the following Directors does not have a material relationship with Aon and is independent under the categorical standards adopted by the Board, applicable legal requirements and the rules of the NYSE: Mr. Conti, Ms. Francis, Mr. Green, Mr. Jannotta, Mr. Kalff, Mr. Knight, Mr. Losh, Mr. Martin, Mr. McKenna, Mr. Morrison, General Myers, Mr. Notebaert, Mr. Rogers, Ms. Santona and Dr. Woo. Mr. Case is considered a management Director because of his position as President and Chief Executive Officer of Aon.

        In determining that each of the non-employee Directors is independent, the Board also considered the following relationships that it deemed were immaterial to such Director's independence.

        With respect to Mr. Conti, Mr. Jannotta, Mr. Knight, Mr. Martin, Mr. McKenna, Mr. Rogers, Ms. Santona and Dr. Woo, the Board considered that, in the ordinary course of business, Aon has sold services to a company (or other entity) at which these Directors is an executive officer (or, in the case of Mr. Martin, is Of Counsel and a retired Partner, and in the case of Dr. Woo, is Dean of the College of Business), and in each case, the amount received from the entity in any of the previous three fiscal years was substantially below one percent (1%) of Aon's annual revenue.

        With respect to Mr. Martin, the Board considered that, in the ordinary course of business, Aon has purchased services from an entity at which Mr. Martin is Of Counsel and a retired Partner, and the amount paid to this entity in any of the previous three fiscal years was substantially below one percent (1%) of the entity's annual revenue.

        With respect to Mr. Knight, the Board considered personal investments made by Mr. Jannotta and Mr. McKenna, as well as by the Aon Pension Fund, in a privately held fund managed by Mr. Knight. The Board determined that the investments were immaterial and did not impair the independence of any non-management Director.

        The Board considered that Mr. Knight, Mr. Martin, Mr. McKenna, Mr. Morrison and Mr. Rogers serve on the boards of various not-for-profit entities with certain executive officers of Aon.

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        With respect to Mr. Jannotta, Mr. Knight, Mr. Martin, Mr. McKenna, Mr. Morrison, General Myers, Mr. Notebaert, Mr. Rogers and Ms. Santona, the Board considered that Aon made charitable contributions in 2010 to certain organizations in which the Director or a Director's spouse serves as an officer, director or trustee. The Board determined that such contributions were immaterial and did not impair the independence of any non-management Director.

        With respect to Ms. Francis, the Board considered the relationship between Aon Hewitt and a non-profit entity of which Ms. Francis serves as co-Chair, in connection with a program designed to promote the development and advance the careers of high-potential female executives. This relationship existed prior to the Hewitt acquisition, and was terminated effective January 1, 2011.

Majority Voting

        Aon's by-laws require that Directors be elected by majority vote in uncontested elections. In January 2009, the Board approved an amendment to Aon's by-laws to provide that, in a contested election, Directors will be elected by plurality vote. In addition, in March 2009, the Board adopted revisions to the Governance Guidelines requiring any incumbent Director who fails to receive a majority of the votes cast in an uncontested election to immediately offer to tender his or her resignation to the Board. The Board will then determine, through a process overseen by the Governance/Nominating Committee, whether to accept the resignation, reject the resignation, or take other action. The Board will act on the recommendation of the Governance/Nominating Committee, and promptly disclose its decision and the rationale behind such decision in a Form 8-K filed with the SEC.

Board Meetings

        The Board met fourteen times in 2010. All incumbent Directors attended at least seventy-five (75%) of the meetings of the Board and all Committees of the Board on which they served. As a result of the ownership interest in Hewitt held by Ariel Investments, LLC, Mr. Rogers was recused from certain Board and Committee meetings at which Aon's acquisition of Hewitt was discussed.

Meetings of Non-Management Directors

        In accordance with NYSE rules and the Governance Guidelines, non-management Directors meet regularly in executive session without management. Lester B. Knight, Aon's non-Executive Chairman, chairs these executive sessions.

Stock Ownership Guidelines

        In July 2006, the Board of Directors adopted Stock Ownership Guidelines for Aon's senior executives and Stock Ownership Guidelines for Non-Management Directors that were each updated and revised in July 2008 and further revised in September 2010. Additional information on the Stock Ownership Guidelines for Aon's senior executives can be found under the heading "Stock Ownership Guidelines" in the section captioned "Compensation Discussion and Analysis."

        Effective January 1, 2011, the Stock Ownership Guidelines for Non-Management Directors require each non-management Director to hold an investment position in Common Stock equal to five times the annual Director retainer. The Guidelines provide a transition period of five years for non-management Directors to achieve the ownership guidelines level; provided, however that each new non-management Director is expected to hold 1,000 shares of Common Stock within the first year of

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joining the Board or transitioning from a management Director to a non-management Director. In addition to shares held directly, vested deferred stock units and shares credited to deferred accounts will be included when determining if the target ownership level has been achieved.

Attendance at Annual Meeting

        The Governance Guidelines provide that Directors are expected to attend the Annual Meeting of Stockholders. All of our Board members serving at the time attended the 2010 Annual Meeting of Stockholders held on May 21, 2010.

Communications with the Board of Directors

        Stockholders and other interested parties may communicate with the Board of Directors by contacting the non-management Directors of Aon Corporation, c/o Office of the Corporate Secretary, 200 East Randolph Street, Chicago, IL 60601. Alternatively, stockholders and other interested parties may communicate with Aon's non-management Directors via electronic mail to the following address: corporate.governance@aon.com.

        The non-management Directors have established procedures for handling communications from stockholders and other interested parties. Communications are distributed to the Chairman of the Governance/Nominating Committee, the full Board of Directors, the non-management Directors or to any individual Director or Directors as appropriate, depending on the facts and circumstances outlined in the communication. Solicitations, spam, junk mail and mass mailings, resumes and other forms of job inquiries, business solicitations or advertisements and frivolous or inappropriate communications will not be forwarded, but will be made available to any non-management Director upon request.

Code of Business Conduct/Code of Ethics for Senior Financial Officers

        The Board has adopted a code of business conduct that applies to our Directors, officers and employees. The Code of Business Conduct can be found on our web site at http://www.aon.com/about-aon/corporate-governance/guidelines-policies/code-of-business-conduct.jsp and is available in print copy to any stockholder who makes a written request to the Office of the Corporate Secretary.

        In addition, the Board has adopted a Code of Ethics for Senior Financial Officers that applies to the principal executive officer and the senior financial officers of Aon and our subsidiaries. The Code of Ethics for Senior Financial Officers can be found on our web site at http:///www.aon.com/about-aon/corporate-governance/guidelines-policies/code-of-ethics-for-senior-financial-officers.jsp.

        We intend to disclose future amendments to, or waivers from, certain provisions of both the Code of Business Conduct and the Code of Ethics for Senior Financial Officers on our website promptly following the date of such amendment or waiver.

Board Leadership Structure and Role in Risk Oversight

        Since April 4, 2005, the positions of Chief Executive Officer and Chairman of the Board of Directors have been held by separate individuals. On April 4, 2005, Gregory C. Case was named Aon's President and Chief Executive Officer, and Patrick G. Ryan, who had served as Aon's Chief Executive Officer prior to that time, became the Executive Chairman of Aon's Board of Directors. After having served as Aon's Chief Executive Officer since 1982 and as Aon's Chairman since 1990, Mr. Ryan moved into the Executive Chairman position to continue to provide executive leadership to Aon and to facilitate the transition of the management of day-to-day operations to Mr. Case. Effective August 1,

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2008, upon the retirement of Mr. Ryan, Lester B. Knight was elected Non-Executive Chairman of Aon's Board of Directors. The position of Non-Executive Chairman is independent from Aon management. As Non-Executive Chairman, Mr. Knight sets the agendas for and presides over the Board meetings and also chairs executive sessions of the non-management Directors of the Board. The Chief Executive Officer is also a member of the Board and participates in its meetings. The Board of Directors believes the separation of the positions of Chief Executive Officer and Chairman is the appropriate structure at this time, as it allows the Chief Executive Officer to focus on the management of Aon and the Chairman to ensure that the Board is focused on its oversight responsibilities, including independent oversight of Aon management.

        Risk is inherent with every business, and how well a business manages risk can ultimately determine its success. We face a number of risks, including economic risks, financial risks, legal and regulatory risks, and others, such as the impact of competition. Management is responsible for the day-to-day management of risks that Aon faces, while the Board of Directors, as a whole and through its Committees, has responsibility for the oversight of risk management. In its risk oversight role, Aon's Board of Directors has the responsibility to satisfy itself that the risk management processes designed and implemented by management are adequate and functioning as designed.

        The Board believes that establishing the right "tone at the top" and full and open communication between management and the Board are essential for effective risk management and oversight. Senior management attends Board meetings and is available to address any questions or concerns raised by the Board on risk management-related and any other matters. The Board of Directors receives presentations from senior management on strategic matters involving our operations.

        While the Board is ultimately responsible for risk oversight at Aon, Aon's Board Committees assist the Board in fulfilling its oversight responsibilities in certain areas of risk. The Board of Directors has delegated to the Audit Committee through its charter the primary responsibility for the oversight of risks facing Aon. The charter provides that the Audit Committee will discuss guidelines and policies with respect to risk assessment and risk management and will discuss Aon's major financial risk exposures and the steps management has taken to monitor and control such exposures. The Audit Committee also has general oversight responsibility for Aon's compliance with legal, regulatory and ethics requirements, which represent many of the most significant risks that Aon faces. The Audit Committee annually reviews legal, regulatory and ethics policies and programs, including Aon's Code of Business Conduct. In addition, the Audit Committee periodically reviews with Aon management any material correspondence with, or other action by, regulators or governmental agencies, and also periodically reviews with Aon's General Counsel legal matters that may have a material impact on Aon's financial statements or compliance policies. Aon's senior management periodically reviews with the Audit Committee the major risks facing Aon and the steps management has taken to monitor and mitigate those risks.

        In light of the breadth and number of responsibilities that the Audit Committee must oversee, and the importance of the evaluation and management of risk related to Aon's compliance programs and policies, the Board formed the Compliance Committee, which is currently a standing subcommittee of the Audit Committee, to oversee Aon's implementation of compliance policies, programs and procedures that are designed to be responsive to the various compliance and regulatory risks facing Aon and to assist the Audit Committee in fulfilling its oversight responsibility for Aon's legal, regulatory and ethics policies and programs. In addition to its general oversight of Aon's legal and regulatory compliance policies, programs and procedures, the Compliance Committee is also

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responsible for the ongoing monitoring of Aon's efforts towards transparency and disclosure of its compensation business practices related to compensation from insurers.

        While the Board's primary oversight of risk is with the Audit Committee, the Board has delegated to other Committees the oversight of risks within their areas of responsibility and expertise. For example, the Organization and Compensation Committee reviews the risks associated with Aon's compensation practices, including an annual review of Aon's risk assessment of its compensation policies and practices for its employees. The Finance Committee reviews significant financial exposures and contingent liabilities of Aon, including Aon's capital structure, its credit ratings and its cost of capital, long-term benefit obligations, and Aon's use of or investment in financial products, including derivatives used to manage risk related to foreign currencies, commodities, and interest rates. In addition, the Finance Committee reviews certain proposed mergers, acquisitions and divestitures; monitors the financial performance of completed mergers and acquisitions; and oversees the financial, investment and actuarial policies and objectives of Aon's ERISA-qualified benefit plans, reviews the investment performance of those plans, and periodically reviews the investment performance of, and makes recommendations regarding investment guidelines for, non-U.S. benefit and retirement plans. The Finance Committee also reviews Aon's major insurance programs. The Governance/Nominating Committee oversees the risks associated with Aon's overall governance and its succession planning process to confirm that Aon has a slate of future, qualified candidates for key management positions.

        The Board believes that its oversight of risks, primarily through delegation to the Audit Committee, but also through delegation to other Committees to oversee specific risks within their areas of responsibility and expertise, and the sharing of information with the full Board, is appropriate for a company like Aon that serves clients through its risk solutions business, acting as an advisor and insurance and reinsurance broker, and human resources solutions business, partnering with organizations to solve their most complex benefits, talent and related financial challenges. The Chair of each Committee that oversees risk provides a summary of the matters discussed with the Committee to the full Board following each Committee meeting. The minutes of each Committee meeting are also provided to all Board members.

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BOARD OF DIRECTORS AND COMMITTEES

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        The Board of Directors has appointed standing Committees, including Executive, Audit, Governance/Nominating, Finance and Organization and Compensation Committees. The Audit Committee has also established the Compliance Committee as a standing sub-committee of the Audit Committee. The charters of the Audit, Compliance, Governance/Nominating, Finance and Organization and Compensation Committees are available on the corporate governance section of our website at http://www.aon.com/about-aon/corporate-governance/guidelines-policies/board-committees-charters.jsp. The Governance Guidelines are also available on the corporate governance section of our website at http://www.aon.com/about-aon/corporate-governance/guidelines-policies/aon-corporation-governance-guidelines.jsp.

        Membership on the Committees since the last Annual Meeting in 2010 has been as follows:

Executive Committee

        When the Board of Directors is not in session, the Executive Committee is empowered to exercise the power and authority in the management of the business and affairs of Aon as would be exercised by the Board of Directors, subject to certain exceptions. The Executive Committee acted by unanimous written consent on four occasions in 2010.

Audit Committee

        In 2010, the Audit Committee met seven times. The Board of Directors has determined that each of the members of the Audit Committee is independent as defined by the rules of the NYSE. In addition, as required by the rules of the NYSE, all of the Committee members are financially literate. The Board of Directors has also determined that each of J. Michael Losh, the Chairman of our Audit Committee, Fulvio Conti, Judson C. Green, Robert S. Morrison, Richard C. Notebaert and John W. Rogers, Jr. is an "audit committee financial expert" within the meaning of rules promulgated by the SEC. The primary purposes of the Audit Committee are to assist the Board with the oversight of: (i) the integrity of Aon's financial statements and financial reporting process; (ii) Aon's compliance with legal and regulatory requirements and ethics programs established by management and the Board; (iii) the engagement of the independent auditor, and its qualifications, independence and performance; and (iv) the performance of Aon's internal audit function. In discharging this role, the Audit

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Committee is authorized to retain outside counsel or other experts as it deems appropriate to carry out its duties and responsibilities.

        The Board has considered Mr. Losh's service as a member of other audit committees, and determined that Mr. Losh's simultaneous service on the audit committees of more than two other public companies does not impair his ability to effectively serve on our Audit Committee. In reaching this determination, the Board considered Mr. Losh's substantial experience and understanding of public company financial reporting, accounting principles and audit committee functions acquired throughout the course of his professional career, and his availability to devote time and attention to his service on the Audit Committee, as he is not currently serving in an executive officer capacity for another company.

        The Audit Committee charter can be found on the corporate governance section of our website at http://www.aon.com/about-aon/corporate-governance/guidelines-policies/board-charters/amended-restated-audit-committee-charter.jsp. Additional information regarding the Audit Committee's responsibilities may be found in this proxy statement in the section captioned "Report of the Audit Committee."

Compliance Committee

        The Compliance Committee is a standing sub-committee of the Audit Committee, which has general oversight responsibility for Aon's legal, regulatory and ethics policies and programs. The primary purposes of the Compliance Committee are to: (i) oversee Aon's implementation of compliance programs, policies and procedures that are designed to be responsive to the various compliance and regulatory risks facing Aon; (ii) oversee Aon's efforts towards transparency and disclosure of its compensation business practices related to compensation from insurers; and (iii) assist the Audit Committee in fulfilling its oversight responsibilities for Aon's compliance and ethics programs, policies and procedures. The Compliance Committee reports regularly to the Audit Committee regarding its activities. Each member of the Compliance Committee is independent as defined in the independence standards of the NYSE. The Compliance Committee met four times during 2010.

Finance Committee

        The Finance Committee is responsible for assisting the Board with monitoring and overseeing Aon's balance sheet, including Aon's capital management strategy, capital structure, investments, returns and related policies. The Finance Committee also reviews certain proposed mergers, acquisitions and divestitures in accordance with policies established by the Board. In addition, the Finance Committee oversees the financial, investment and actuarial policies and objectives of Aon's ERISA-qualified benefit plans, and reviews the investment performance of non-U.S. benefit and retirement plans. The Finance Committee met three times during 2010.

Governance/Nominating Committee

        The Governance/Nominating Committee identifies and recommends to the Board of Directors candidates for service on the Board, reviews and recommends the renomination of incumbent Directors, reviews and recommends Committee appointments and leads the annual performance evaluation of the Board and its Committees. In addition, the Governance/Nominating Committee develops and recommends governance guidelines for Aon to the Board of Directors, reviews related party transactions, periodically reviews the management succession planning process and periodically

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reviews compliance with stock ownership guidelines. Each member of the Governance/Nominating Committee is independent as defined in the independence standards of the NYSE. The Governance/Nominating Committee met six times during 2010.

        The Governance/Nominating Committee considers recommendations for Director candidates from Aon's Directors and executive officers. In addition, the Governance/Nominating Committee will consider stockholders' recommendations. Recommendations, together with the name and address of the stockholder making the recommendation, relevant biographical information regarding the proposed candidate, and a description of any arrangement or understanding between the stockholder and the proposed nominee, should be sent to our Corporate Secretary. Consistent with the Governance Guidelines, the Governance/Nominating Committee considers a number of criteria in evaluating Director candidates, including professional background, expertise, reputation for integrity, business experience, leadership capabilities and potential contributions to the Board of Directors and Aon's management. The Governance/Nominating Committee also considers whether a potential nominee would satisfy the categorical independence standards adopted by the Board consistent with the NYSE corporate governance standards.

        The Board of Directors also values diversity as a factor in selecting nominees to serve on the Board, and believes that the diversity that exists in its composition provides significant benefits to the Board and Aon. Although there is no specific policy on diversity, the Governance/Nominating Committee considers the criteria noted above in selecting nominees for Directors, including members from diverse backgrounds who combine a broad spectrum of experience and expertise with a reputation for integrity. Such considerations may include gender, race, national origin, functional background, executive or professional experience, and international experience. The effectiveness of the nomination process, including the criteria used for selecting nominees for Directors, is evaluated by the Board each year as part of its annual self-evaluation process and by the Governance/Nominating Committee as it evaluates and identifies Director candidates.

        When a vacancy exists on the Board of Directors due to the expansion of the size of the Board of Directors or the resignation or retirement of an existing Director, the Governance/Nominating Committee identifies and evaluates potential Director nominees. The Governance/Nominating Committee has sole authority to retain and terminate any search firm to be used to identify Director candidates and sole authority to approve such search firm's fees and other retention terms.

        Candidates for Director are evaluated using the criteria discussed above and the existing composition of the Board of Directors, including its size, structure, backgrounds and areas of expertise of existing Directors and the number of independent and management Directors. The Governance/Nominating Committee also considers the specific needs of the various Board Committees. The Governance/Nominating Committee recommends potential Director candidates to the full Board of Directors, which is responsible for final approval of any Director candidate. This process is the same for Director candidates who are recommended by our stockholders.

        Recommendations for Director candidates to stand for election at the 2012 Annual Meeting of Stockholders must be submitted in writing to the Corporate Secretary of Aon, 200 East Randolph Street, Chicago, IL 60601. Recommendations will be forwarded to the Chairman of the Governance/Nominating Committee for review and consideration.

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Organization and Compensation Committee

        The Organization and Compensation Committee (the "Compensation Committee") assists the Board in carrying out its overall responsibilities with regard to executive compensation, including oversight of the determination and administration of Aon's philosophy, policies, programs and plans for executive officers and non-management Directors. The Compensation Committee annually reviews and determines the compensation of Aon's executive officers, including Aon's Chief Executive Officer subject to the input of the independent members of the Board. The Compensation Committee consults with the Chief Executive Officer on, and directly approves, the compensation of other executive officers, including special hiring and severance arrangements. The Compensation Committee administers the Aon Stock Incentive Plan (and its predecessor plans), including granting equity awards (other than awards to the Chief Executive Officer and the Non-Executive Chairman, which awards are approved by the independent members of the Board) and interpreting the plan, and has general administrative responsibility with respect to Aon's other U.S. employee benefit programs. In addition, the Compensation Committee reviews and makes recommendations to the Board concerning Directors' compensation and certain amendments to U.S. employee benefit plans or equity plans. The Compensation Committee also reviews and discusses the compensation disclosures contained in Aon's Annual Report on Form 10-K and proxy statement. The Compensation Committee may delegate its authority to sub-committees when appropriate, although it did not do so in 2010. The Compensation Committee met seven times during 2010. The Compensation Committee charter can be found on the corporate governance section of our website at http://www.aon.com/about-aon/corporate-governance/guidelines-policies/board-charters/organization-compensation-committee-charter.jsp.

Process of Determining Executive Compensation

        The role of Aon's management is to assist the Compensation Committee in managing Aon's executive and Director compensation programs. Direct responsibilities of management include, but are not limited to:

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Recommending compensation increases, short and long-term incentive awards and, where applicable, severance benefits for executive officers other than the Chief Executive Officer;



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Providing an ongoing review of the effectiveness of Aon's compensation programs and aligning the programs with Aon's objectives;



•

Designing and recommending the amendment of long-term and short-term cash and equity-based incentive plans; and



•

Designing and recommending the amendment of U.S. employee benefit plans.

        In the first quarter of 2011, the independent Directors evaluated the performance, and reviewed the compensation, of the Chief Executive Officer. At that time, the Compensation Committee also evaluated the performance and reviewed the compensation of all other executive officers. The Compensation Committee also approved for each executive officer a target annual incentive for 2011 performance and the specific corporate performance metric that Aon's performance would be measured against for 2011.

        In connection with this annual compensation review, management presented the Compensation Committee with compensation tally sheets reporting compensation paid for 2010 and competitive pay data, where available, as a market check. The Compensation Committee also reviewed and considered the overall performance of Aon against a target that was established for 2010 culminating in certain

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compensation decisions made by the Compensation Committee during the first quarter of 2011. The Compensation Committee's decisions with respect to the compensation of our executive officers are described in this proxy statement in the section captioned "Compensation Discussion and Analysis."

Relationship with Executive Compensation Consultant

        Since 2005, the Compensation Committee has retained Frederic W. Cook & Co., Inc. as its independent executive compensation consultant. The consultant provides expertise on various matters coming before the Compensation Committee. The consultant is engaged by, and reports directly to, the Compensation Committee. The consultant does not advise Aon's management or receive other compensation from Aon. George Paulin, the Chief Executive Officer of Frederic W. Cook & Co., Inc., typically participates in all meetings of the Compensation Committee during which executive compensation matters are discussed and communicates between meetings with the Chairman of the Compensation Committee. During 2010, the consultant assisted the Compensation Committee by: providing insights and advice regarding Aon's compensation philosophy, objectives and strategy; developing criteria for identification of Aon's peer group for executive compensation and company performance review purposes; reviewing management's proposals for the design of short-term cash and long-term equity incentive compensation programs; providing insights and advice regarding Aon's analysis of the risks arising from its compensation policies and practices; and advising on and providing comments on management's recommendations regarding executive officers' bonuses for 2010 and equity-based awards granted in 2010. Management periodically retains other consulting firms to provide pay survey data and other non-executive compensation services that may be presented to or reviewed by the Compensation Committee.

Review of Compensation Policies and Practices

        Although recently there has been increased scrutiny of risk and whether companies' compensation programs contribute to unnecessary risk taking, we believe that we have historically maintained a level of prudence associated with our compensation programs and will continue to do so. We engage in a process to evaluate whether our executive and broad-based compensation programs contribute to unnecessary risk-taking and have concluded that the risks arising from these programs are not reasonably likely to have a material adverse effect on Aon.

Compensation Committee Interlocks and Insider Participation

        During 2010, the Compensation Committee was composed of Richard C. Notebaert (Chairman), Cheryl A. Francis, Edgar D. Jannotta, J. Michael Losh, Andrew J. McKenna, Robert S. Morrison and Richard B. Myers. No member of the Compensation Committee was, during 2010 or previously, an officer or employee of Aon or any of its subsidiaries. In addition, during 2010, there were no compensation committee interlocks required to be disclosed.

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REPORT OF THE AUDIT COMMITTEE

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        The Audit Committee oversees Aon's financial reporting process on behalf of the Board of Directors. Management has the primary responsibility for establishing and maintaining adequate internal financial controls, for preparing the financial statements and for the reporting process. Ernst & Young LLP ("E&Y"), Aon's independent registered public accounting firm for 2010, is responsible for expressing opinions on the conformity of Aon's audited financial statements with generally accepted accounting principles and the effectiveness of Aon's internal control over financial reporting.

        In this context, the Audit Committee reviewed and discussed with management and E&Y the audited financial statements for the year ended December 31, 2010, as well as management's assessment of the effectiveness of Aon's internal control over financial reporting and E&Y's evaluation of Aon's internal control over financial reporting. The Audit Committee has discussed with E&Y the matters that are required to be discussed by Auditing Standards, the SEC and other regulatory agencies (Communication with Audit Committees).

        In addition, the Audit Committee has discussed with E&Y the independence of that firm from Aon and its management, including the matters in the written disclosures required by Rule 3526 of the Public Company Accounting Oversight Board (Communication with Audit Committees Concerning Independence). The Audit Committee has also considered whether E&Y's provision of non-audit services to Aon is compatible with maintaining E&Y's independence. The Audit Committee has concluded that E&Y is independent from Aon and its management.

        The Audit Committee discussed with Aon's internal auditors and E&Y the overall scope and plans for their respective audits. The Audit Committee meets with the internal and independent auditors, with and without management present, to discuss the results of their examinations, their evaluations of Aon's internal controls, and the overall quality of Aon's financial reporting.

        In reliance on the reviews and discussions referred to above, and subject to the limitations on the role and responsibilities of the Audit Committee referred to above, the Audit Committee recommended to the Board of Directors (and the Board has approved) that the audited financial statements be included in the Annual Report on Form 10-K for the year ended December 31, 2010 for filing with the SEC. The Audit Committee has approved, and the Board of Directors has requested that stockholders ratify, the selection of E&Y as our independent registered public accounting firm for the year 2011.

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PROPOSAL 2—RATIFICATION OF APPOINTMENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

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        The Audit Committee has appointed E&Y as Aon's independent registered public accounting firm for the year 2011, subject to ratification by our stockholders. E&Y was first retained as Aon's independent registered public accounting firm in February 1986. Although this appointment is not required to be submitted to a vote of the stockholders, the Board of Directors believes it appropriate as a matter of policy to request that the stockholders ratify the appointment of the independent registered public accounting firm for the year 2011. In the event this proposal does not receive the affirmative vote of the holders of a majority of the shares entitled to vote and present in person or represented by proxy at the Annual Meeting, the Audit Committee will reconsider the appointment, but may decide to maintain its appointment of E&Y.

        We anticipate that a representative of E&Y will be present at the Annual Meeting. The representative will be given the opportunity to make a statement if he or she desires to do so, and is expected to be available to respond to any appropriate questions that may be submitted by stockholders at the Annual Meeting.

        OUR BOARD OF DIRECTORS AND AUDIT COMMITTEE UNANIMOUSLY RECOMMEND THAT YOU VOTE "FOR" THE RATIFICATION OF THE APPOINTMENT OF ERNST & YOUNG LLP AS OUR INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM FOR 2011.

        Audit Fees.    Fees for audit services totaled approximately $18.5 million in 2010 and $17.9 million in 2009. For both years, audit fees included services associated with the annual audit, including fees related to Sarbanes-Oxley Section 404, the reviews of Aon's documents filed with the SEC, and statutory audits required domestically and internationally.

        Audit-Related Fees.    Fees for audit-related services totaled approximately $1.9 million in 2010 and $1.6 million in 2009. Audit-related fees include services such as employee benefit plan audits, other attestation services, due diligence in connection with acquisitions and accounting consultations not included in audit fees.

        Tax Fees.    Fees for tax services, including tax compliance, tax advice and tax planning totaled approximately $1.7 million in 2010 and $2.2 million in 2009.

        All Other Fees.    Fees for all other services not included above totaled $0 in each of 2010 and 2009.

Audit Committee's Pre-Approval Policies and Procedures

        The Audit Committee pre-approves all audit and permissible non-audit services provided by the independent registered public accounting firm. These services may include audit services, audit-related services, tax services and other services. Each pre-approval provides details regarding the particular service or category of service to be provided and is subject to a specific engagement authorization. The Audit Committee requires that the independent registered public accounting firm and management report on the actual fees charged by the independent registered public accounting firm for each category of service at Audit Committee meetings held during the year.

        The Audit Committee acknowledges that circumstances may arise throughout the year that require the engagement of the independent registered public accounting firm to provide additional services not contemplated in the Audit Committee's initial pre-approval process that occurs on an annual basis. In those circumstances, the Audit Committee requires that specific pre-approval be obtained before

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engaging the independent registered public accounting firm. The Audit Committee has delegated pre-approval authority to the Chairman of the Audit Committee for those instances when pre-approval is needed prior to a scheduled Audit Committee meeting. Such pre-approvals are reported to the Audit Committee at the next scheduled Audit Committee meeting.

        All audit and non-audit services provided by the independent registered public accounting firm during 2010 were pre-approved in accordance with Aon's pre-approval policy as described above.

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COMPENSATION COMMITTEE REPORT

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        The Organization and Compensation Committee of the Board of Directors of Aon has reviewed and discussed with management the Compensation Discussion and Analysis required by Item 402(b) of Regulation S-K and set forth in this proxy statement.

        Based on its review and discussions with management, the Organization and Compensation Committee recommended to the Board of Directors that the Compensation Discussion and Analysis be included in this proxy statement and Aon's Annual Report on Form 10-K.

        This Report is provided by the Organization and Compensation Committee, which is composed entirely of the following independent Directors:

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EXECUTIVE COMPENSATION

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Compensation Discussion and Analysis

Introduction

        This Compensation Discussion and Analysis ("CD&A") describes and analyzes our executive compensation program. It should be read in conjunction with the executive compensation tables and corresponding footnotes that follow, as it provides context for the amounts shown in the tables and the footnote disclosures.

        This CD&A is arranged in the following four sections:

•

Executive Summary of the CD&A



•

Discussion of our compensation objectives and process



•

Explanation of compensation components and analysis of 2010 pay decisions



•

Other policies and practices as they relate to our executive compensation program

        While the discussion focuses primarily on compensation awarded to our named executive officers, we address Aon's compensation programs as they apply to other employees where it enhances an understanding of our compensation philosophy. In this proxy statement, the reference to our "named executive officers" means Gregory C. Case, our President and Chief Executive Officer (our "CEO"); Christa Davies, our Executive Vice President and Chief Financial Officer (our "CFO"); Russell P. Fradin, Stephen P. McGill and Michael J. O'Connor, our three other most highly compensated executive officers for 2010; and Baljit Dail and Andrew M. Appel, who would have been among our most highly compensated executive officers except that they were not serving as executive officers as of December 31, 2010.

Executive Summary

        Who We Are    We are a global professional services firm with over 59,000 employees worldwide focused exclusively on risk and people. We are the industry-leading advisor on risk solutions, both retail and reinsurance, and human resources solutions. We have a presence in over 120 countries with more than 500 offices.

        Our Performance    In 2010 we delivered strong financial results despite a continuing soft market and very challenging economic environment. Net income attributable to Aon stockholders from continuing operations increased 12% per share.

        We continued to execute on our goals of strategically investing in long-term growth, managing expenses and effectively allocating capital. We further aligned our core product portfolio around risk advice and human capital solutions, including the transformative acquisition of Hewitt on October 1, 2010. In acquiring Hewitt, we not only solidified our leading position in HR solutions but also significantly increased our revenues, expanded our product and service offerings globally and increased our cash flow from operations in the U.S. As a result, we believe we are well positioned for long-term value creation.

        Against a multi-year backdrop of weak economic conditions globally, we view our longer range results as particularly impressive compared to the results of our industry peers and the benchmark S&P 500. Over the last three calendar years, our stock price return was a positive 37%, compared to

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the returns of our primary industry peers, including Marsh & McLennan Companies, Inc. (which declined 1%) and Willis Group Holdings Limited (which declined 2%), as well as the benchmark S&P 500 (which declined 11%). In addition, as compared to our Global Industry Classification Standard ("GICS") code peers in the insurance industry, our three-year relative total stockholder returns are at or above median. We returned $425 million of excess capital to stockholders through our share repurchase program and dividends, highlighting our strong cash flow generation and effective allocation of capital.

        Our Compensation    We awarded our named executive officers for their dedication and achievement in 2010 with compensation directly linked to performance. Namely:

•

Nearly 93% of Mr. Case's total direct compensation for 2010 was performance-based compensation.



•

While Mr. Case's total direct compensation increased year over year, the increase was due exclusively to the size of the performance-based equity incentive award granted to him in the first quarter of 2010. A significant portion of the award was intended to recognize Mr. Case's commitment to Aon, effective in the fourth quarter of 2009, in entering into a five-year renewal of his employment contract and an amended and restated change-in-control agreement that significantly reduced the financial protection to be afforded to Mr. Case in the event of a termination of his employment in connection with a change-in-control of Aon. The new change-in-control agreement not only removed excise tax gross-up protection from Mr. Case's change-in-control benefits but also capped Mr. Case's cash and non-equity award payments to the "safe harbor" amount under Code Section 280G of the Internal Revenue Code of 1986, as amended (the "Internal Revenue Code"), such that no amounts are payable if Aon cannot deduct them. No adjustments were made to Mr. Case's base salary or annual bonus target from the levels previously established in 2005 and 2009, respectively.



•

Aon's performance was the principal consideration for the bonuses awarded for 2010. With respect to 2010, Mr. Case received an annual bonus of $3,000,000. This represents 100% of his 2010 target annual bonus and 97% of his funded bonus amount. The remaining named executive officers (excluding Mr. Fradin, who did not participate in Aon's bonus program during 2010, and Mr. Appel, who was ineligible for a bonus pursuant to the terms of his separation from Aon) received, on average, 121% of their target annual bonuses and 117% of their funded bonus amounts.



•

In early 2011 we settled performance share units granted to certain of our named executive officers in 2008. Those units were linked to 2008-2010 Aon performance. The units were settled, and shares of Common Stock were awarded, at 130% of target due to Aon's strong performance over that three-year period, as measured by cumulative adjusted earnings per share ("EPS") from continuing operations. Our cumulative adjusted EPS for that period materially exceeded the target.



•

In 2010, we granted similar performance share units to each of our named executive officers, the values of which are wholly dependent on Aon's performance.



•

In 2010, we continued to implement our policy of completely eliminating excise tax gross-up protection from our change-in-control agreements. Two of our named executive officers, Mr. Fradin and Mr. McGill, each signed change-in-control agreements that provide no such protection in the event of a change-in-control of Aon. However, Mr. Fradin retains excise tax

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gross-up protection limited to the Hewitt acquisition, which protection was granted to him by Hewitt and continues unmodified. As the employment agreements of our other senior executives are up for renewal or are otherwise materially amended, we intend to eliminate tax gross-up protection from their change-in-control agreements.

•

In 2010, we revised our stock ownership guidelines for our CEO and other executive officers to increase their required investment positions. Effective immediately, our CEO must hold at least six times (up from four times) his base salary and, effective January 1, 2012, each other executive officer must hold at least three times (up from two times) their base salaries. The revised guidelines also set out equity retention rules requiring that certain shares be retained until the required investment position is achieved.

        These and other compensation decisions are explained below.

        We believe our compensation program achieved its purpose in 2010, as described below.

Compensation Objectives and Process

Objectives of our Compensation Program

        We continue our journey to build, and continuously improve upon, the leading risk advice and HR solutions firm in the world. We accomplish this by providing clients with world-class advice, solutions, innovation and execution. To achieve those objectives, we must be the destination of choice for the best talent. Our compensation program supports this vision and business strategy and fundamentally aligns the financial interests of our executives with those of our stockholders. This is true in both our short and long-term programs. We strive to maximize stockholders' return primarily through growth in pre-tax income from continuing operations and adjusted EPS.

        We have a guiding philosophy with regard to our variable components of compensation, such as equity-based awards and annual bonuses. This philosophy dictates that our stockholders should always benefit first before any element of our executives' variable compensation is earned or paid. For example, under our annual bonus program a minimum level of corporate performance must be achieved before any bonus is payable. We carefully set that minimum each year. Even if the minimum level is achieved, the Compensation Committee reserves the sole discretion to exercise negative discretion to the extent it deems reasonable and prudent under the circumstances.

Use of Peer Group as a Market Check of Target Total Direct Compensation

        We set executive compensation at levels that are appropriate and competitive for global professional services firms within our market sector and the general industry marketplace. We review annual financial reports filed by our peer group. We also annually review the levels of executive officer compensation from global pay surveys. For purposes of doing a market check, and not for purposes of doing true benchmarking to specific percentiles, we look at peer group compensation data. We compare the target total direct compensation (defined as base salary plus target bonus plus equity-based awards) for our named executive officers to the target total direct compensation for executives at selected peer companies where job descriptions are sufficiently similar to those of our executives to permit comparison.

        We utilized two peer groups for 2010 compensation decisions. We describe below the time periods during which each peer group was used, the companies that comprise the peer groups and the rationale for updating the peer group in the fourth quarter of 2010.

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        From January 1, 2010 until November 19, 2010, we utilized the same peer group as approved by the Compensation Committee in November of 2009. That group consisted of the following companies:

        The peer group was selected in 2009 based upon three criteria which each one met at such time. They are global financial services industry companies or major consulting firms with whom we compete for executive talent or financial capital. With the exception of Willis Group Holdings, which is a direct competitor, the peer group is generally comprised of companies that are, or were, between one-third and three times our size in revenues. Lastly, each company provides public disclosure regarding its executive compensation. This peer group represents seven financial industry GICS sub-sectors.

        We believe that the selection of a peer group is something that requires reconsideration every year. Therefore, beginning soon after the Hewitt acquisition in the fourth quarter of 2010, we undertook a review of the composition of our peer group. We recognized the impact of the Hewitt acquisition on our business and we wanted to ensure that the manner in which we define our peers remained relevant and that our peer group provided adequate benchmarks. The updated peer group members were selected based upon three criteria. They are global financial services industry companies or major consulting firms with whom we compete for executive talent or financial capital. With the exception of Willis Group Holdings and Towers Watson, which are direct competitors, and Accenture and Aetna, which are industry comparators, the peer group is generally comprised of companies that are between one-fourth and four times our size in average market capitalization (as calculated over the most recent eight quarters to reduce volatility). Lastly, each company provides public disclosure regarding its executive compensation.

        After discussions with its compensation consultant, the Compensation Committee approved the following peer group effective November 19, 2010, for use as a reference point in future compensation decisions:

        Companies continuing from the prior peer group are identified with a "C" and those newly added to this peer group are identified with an "N". This updated peer group represents five financial industry GICS sub-sectors.

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How We Determine Total Compensation

        As described above, market data is helpful in determining the competitive level of various elements of total direct compensation. However, for 2010 we did not generally have a specific market target for the total compensation. We did not specifically target a certain percentile of total compensation or a particular component or subset of compensation with regard to the benchmark. We did not use a specific formula to set total compensation either in relation to market data, the relative mix of pay components or otherwise. A decision regarding one component of compensation had only an indirect link to decisions regarding other pay components.

        We generally targeted a competitive level and mix of total direct compensation elements using market data simply as a reference point. This was not a mechanical process. Rather, we used our judgment and business experience. Overall, our intent was to manage the various elements of total compensation together so that the emphasis of our compensation program was on our variable components of pay, including long term equity awards and annual bonus awards that fluctuate based on the performance of Aon.

        Performance-based compensation for 2010 of our named executive officers employed with us for the full-year (i.e. excluding Mr. Fradin who joined Aon on October 1, 2010 in connection with the Hewitt acquisition) ranged from 56.7%-92.8% of total direct compensation, based on the grant date fair value of the long-term equity awards as valued in accordance with Financial Accounting Standards Board Accounting Standards Codification Topic 718, Compensation—Stock Compensation ("FASB ASC Topic 718"), as follows:

        This supplemental table is not required by the SEC, but rather it is provided to demonstrate the link between performance and our executives' total direct compensation for 2010. Please refer to the Summary Compensation Table for Fiscal Years 2010, 2009 and 2008 for complete disclosure of the total compensation of our named executive officers, reported in accordance with the SEC disclosure requirements.

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        As the chart demonstrates, we strive to link our executive's pay to performance at greater rates for our more senior executives. Given the responsibility of our CEO to drive performance results for Aon, and his success in achieving those results as further described below, 92.8% of Mr. Case's total direct compensation for 2010 was linked directly to the performance of Aon. For 2010, the percentage of total direct compensation awarded as performance-based pay for Mr. Fradin was 44.0% due to his receipt of non-performance based equity awards upon joining Aon, as described below under the heading "Equity-Based Awards—Restricted Stock Units". Mr. McGill's percentage for 2010, 56.7%, was below his 2009 percentage of 80% on account of his receipt in 2010 of a non-performance based bonus, as described below under the heading "Performance-Based Annual Bonus—Mr. McGill's One-Time Transfer Payment".

Our Use of Tally Sheets

        In connection with our annual compensation review process, as described in the section of this proxy statement captioned "Board of Directors and Committees—Organization and Compensation Committee—Process of Determining Executive Compensation," the Compensation Committee reviews compensation tally sheets. The tally sheets assign dollar amounts to each component of the executive's compensation, including outstanding equity awards, current bonus and base salary, deferred compensation, employee benefits (including supplemental pension benefits), perquisites and potential change-in-control severance payments. The tally sheets are presented to the Compensation Committee to ensure it is aware of all compensation elements and the value of such elements.

Involvement of Mr. Case in the Compensation Process

        Each year, the Compensation Committee approves all elements of compensation for Aon's named executive officers and other executive officers. These decisions are typically made during the annual compensation review process conducted in the first calendar quarter. The Compensation Committee solicits certain recommendations from each of Mr. Case and our Global Head of Human Resources.

        Mr. Case recommends to the Compensation Committee the equity award, annual bonus and base salary adjustment, if any, for the executive officers who report directly to him. He has direct knowledge of the contributions made by those executive officers to Aon and he shares this knowledge with the Compensation Committee. Mr. Case supports his recommendations by providing performance evaluations for his direct reports.

        During the annual review process, Mr. Case and the Chairman of the Compensation Committee work together on Mr. Case's annual evaluation report, which summarizes Mr. Case's qualitative and quantitative performance. The report is considered in the determination of Mr. Case's compensation, along with other factors, including the Compensation Committee's own assessment of Mr. Case's performance, relevant market data and Aon's overall performance.

        The Compensation Committee has the ultimate authority to make compensation decisions. The Compensation Committee discusses its preliminary compensation decisions with the independent members of the Board who do not serve on the Compensation Committee. This process garners valuable input from those Directors regarding the executives' performance. The sharing of performance review information also aids the Directors in carrying out their succession planning responsibilities. After considering input from those Directors, the Compensation Committee makes its final determination.

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        Mr. Case, together with our Global Head of Human Resources and our CFO, makes recommendations to the Compensation Committee relating to the corporate performance targets to be established under Aon's Shareholder-Approved Plan (as defined below under "Compensation Components and Analysis of 2010 Pay Decisions—Components of Total Compensation—Performance-Based Annual Bonus") and long-term equity incentive programs. The Compensation Committee reviews such recommendations with its independent executive compensation consultant and reserves the ultimate authority to set such targets and to determine whether such goals were achieved.

Compensation Components and Analysis of 2010 Pay Decisions

Components of Total Compensation

        The table below describes our rationale for providing each of the key components of our executive compensation program and the factors that we consider in determining the amounts for a given year.

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Equity-Based Awards

        The Aon Stock Incentive Plan, as amended and restated in 2006 and as further amended from time to time (the "Stock Plan"), authorizes the grant of a variety of equity compensation awards. Among other types of awards, it authorizes the issuance of performance share unit awards and restricted stock units—the two forms of equity compensation granted to our named executive officers in 2010. Stock options were not featured in our performance-based equity programs in 2010, as explained below.

        Performance Share Unit Awards    In the first quarter of 2010, we granted performance share units to our executive officers, including each named executive officer other than Mr. Fradin, pursuant to the fifth cycle of our "Leadership Performance Program" ("LPP 5"). LPP 5 is a sub-plan of the Stock Plan. This program is the fifth layer of consecutive three-year performance cycles for certain of our named executive officers. It is intended to further strengthen the relationship between capital accumulation for our executives and long-term Aon financial performance and stockholder value.

        The performance share units awarded under LPP 5 are payable in shares of Common Stock. The nominal value of the awards was determined and approved by the Compensation Committee. The number of target performance share units was calculated on the date of grant based on that day's closing price of Common Stock, in accordance with the terms of the Stock Plan. Additional terms and conditions applicable to the performance share units, including the treatment of performance share units upon the occurrence of various termination events, are described in the section captioned "Potential Payments on Termination or Change-in-Control" contained in this proxy statement.

        The performance share units under LPP 5 will be earned and settled in a range of 0% to 200% of target value based on performance results over a three-year performance period. The performance period began January 1, 2010, and will end on December 31, 2012. The performance results will be measured against the specified cumulative adjusted EPS target for 2010-2012. After adjustments, the cumulative target ranges from $9.25, below which no payout will occur, to $10.82, which would yield a payout of 200% of the target award value. A result of $9.67 in cumulative adjusted EPS would yield a payout, and settlement in shares of Common Stock, at 100% of target. This target represents a 4.5% increase over the adjusted baseline for the fourth cycle of our Leadership Performance Program established for the performance period 2009-2011 ("LPP 4"). The target represents a challenging, yet achievable, performance goal.

        Award Values and Features    In determining the individual awards under LPP 5, the Compensation Committee reviewed peer group market data, where available, for each executive to determine the

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appropriate long-term value of such awards. For example, the market data relevant to Mr. Case supported a larger award to him than the awards granted to the other named executive officers.

        In addition, as described in our proxy statement for the 2010 Annual Meeting of Stockholders, Mr. Case was awarded an additional award valued at $10 million under LPP 5 to be earned on the same performance criteria and weightings as his regular award. A significant portion of the award was intended to recognize Mr. Case's commitment to Aon, effective in the fourth quarter of 2009, in entering into a five-year renewal of his employment contract and an amended and restated change-control agreement that significantly reduced the financial protection to be afforded to Mr. Case in the event of a termination of his employment in connection with a change-in-control of Aon. The new change-in-control agreement not only removed excise tax gross-up protection from Mr. Case's change-in-control benefits but also capped Mr. Case's cash and non-equity award payments to the "safe harbor" amount under Section 280G of the Internal Revenue Code, such that no amounts are payable if Aon cannot deduct them.

        The Compensation Committee determined that performance share units should be the exclusive form of award under LPP 5 (as opposed to a mix of performance share units and stock options under earlier versions of the program) because performance share units utilize fewer shares of our Common Stock and are, therefore, a more efficient form of award while allowing us to maintain a strong performance focus.

        The Compensation Committee's selection under LPP 5 of the three-year performance period and cumulative adjusted financial performance metric provides the award recipients a reasonable period of time within which to achieve and sustain challenging long-term growth objectives. The Compensation Committee believes adjusted EPS more effectively aligns executives to improve Aon performance, rather than EPS calculated in accordance with GAAP, as the adjusted measure provides a more certain target that is within their control and area of accountability, and is a better measure of operating performance long-term.

        Awards under LPP 5 are subject to forfeiture under certain circumstances. In the event an award recipient voluntarily terminates employment or is terminated by Aon for cause prior to the scheduled vesting date, none of the performance share units will vest and the entire award will be forfeited.

        The Compensation Committee did not consider the number or value of equity-based awards previously granted to, or currently held by, any of our named executive officers in determining individual awards for 2010. Past awards were granted to induce performance in prior years. As a result, they were not viewed as significant in determining the 2010 awards to the named executive officers.

        Settlement of LPP 3    In early 2011, we determined the actual achievement under the third cycle of our Leadership Performance Program, covering the performance period January 1, 2008 through December 31, 2010 ("LPP 3"). We settled the performance share units in shares of Common Stock. The cumulative adjusted EPS from continuing operations target ranged from $8.35, below which no payout was due to occur, to $9.70, which would have yielded a payout at 200% of the target award value. A result of $8.85 in cumulative adjusted EPS from continuing operations would have yielded a payout at 100% of target. This target represented a 14% increase over the adjusted baseline for the second cycle of our Leadership Performance Program established for the performance period 2007-2009 ("LPP 2"). Our actual cumulative adjusted EPS from continuing operations for the three-year period were $9.15, resulting in a payout at 130% of target.

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        The annual EPS from continuing operations results for LPP 3 include adjustments detailed by the plan governing LPP 3 and approved by the Compensation Committee. For each year of the performance period associated with LPP 3 adjustments to EPS from continuing operations were approved by the Compensation Committee because they were significant one-time transactions or outside management's control, as follows: charges associated with our restructuring plans; write-down of deferred taxes related to changes in future statutory tax rates and the amendment of the APB exemption status of Combined Insurance Company of America ("CICA") following sale announcement; gains on sale of land, businesses or discontinued operations; costs related to our acquisition of Benfield and sale of CICA; operating results of discontinued operations held for sale before sale closing; pension curtailment gain/loss net of tax; costs related to our acquisition of Hewitt; and an adjustment to results related to the Hewitt acquisition. Any permissible adjustment will be made on a comparable basis across the other Leadership Performance Programs then in progress. Each of our named executive officers other than Mr. Fradin, participated in LPP 3.

        We do not pay dividends or dividend equivalents on performance share units.

        LPP 6    In connection with the Hewitt acquisition, Aon entered into an employment agreement with Mr. Fradin on September 30, 2010, which agreement is described in the narrative section captioned "Employment Agreements and Other Compensation Arrangements" that follows the Grants of Plan-Based Awards in Fiscal Year 2010 table and in the section captioned "Potential Payments on Termination or Change-in-Control." To provide significant incentive for Mr. Fradin's retention, and to ensure the performance-based nature of such incentive, the agreement committed Aon to provide Mr. Fradin with an award valued at $2 million under the sixth cycle of our leadership performance program established for the performance period beginning January 1, 2011 and ending December 31, 2013 ("LPP 6"). The award will be earned based on the achievement of a cumulative adjusted EPS target. Because this non-contingent commitment was made to Mr. Fradin during 2010, the award is reported in the Grants of Plan-Based Awards in Fiscal Year 2010 table in this proxy statement.

        In connection with Mr. McGill's employment agreement with Aon, effective November 18, 2010, Aon committed to provide Mr. McGill an additional award under LPP 6 of $6 million in value, subject to approval of such award by the Compensation Committee. The $6 million additional award was subsequently approved by the Compensation Committee on March 17, 2011. As this action was taken after the close of the 2010 fiscal year, the award will be reported in the proxy statement for the 2012 Annual Meeting of Stockholders, and is not reflected in the Grants of Plan-Based Awards in Fiscal Year 2010 table in this proxy statement.

        Aon Hewitt Performance Program    Mr. Fradin's employment agreement also provides that he will receive an award under the Aon Hewitt Performance Program established for the performance period beginning January 1, 2011 and ending December 31, 2013 (the "AHPP"). The award was valued at $2 million and will be earned based on the achievement of a cumulative adjusted pre-tax income target for the Aon Hewitt segment. In approving such award, the Compensation Committee considered the retentive and performance-based nature of the award, Mr. Fradin's significant management responsibility for our Aon Hewitt segment, and the intended purpose of the AHPP, which is to perform as a management integration tool that will align senior leaders from Hewitt with our legacy consulting unit under a common performance-based long-term equity incentive program. Because this non-contingent commitment was made to Mr. Fradin during 2010, the award is reported in the Grants of Plan-Based Awards in Fiscal Year 2010 table in this proxy statement.

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        Restricted Stock Units    In the first quarter of 2010, we granted time-vested restricted stock units to each of our named executive officers other than Mr. Fradin in connection with Aon's Incentive Stock Program (the "ISP"). The ISP provides executives with a portion of their annual bonus in the form of restricted stock units, thereby making the entitlement to such time-vested restricted stock units wholly dependent on performance. The primary goals of the ISP are to further focus the employees' attention on the longer-term performance of Aon as a whole, and to further promote employee retention and stock ownership.

        No other time-vested equity awards were granted to our named executive officers, with the exception of the restricted stock units granted to Mr. Fradin in connection with his retention by Aon following the Hewitt acquisition. Those restricted stock units were intended to incentivize Mr. Fradin to remain with Aon post-acquisition instead of terminating his employment relationship to collect the change-in-control benefits to which he was otherwise entitled in connection with the acquisition. Mr Fradin was awarded $2 million in restricted stock units, which will vest over five years. In addition, Mr. Fradin agreed to convert approximately $5 million otherwise payable to him upon his departure from Hewitt (or its successor) in a change-in-control transaction pursuant to Hewitt's Amended and Restated Change-in-Control Executive Severance Plan into Aon restricted stock units, all of which are fully vested and will be distributed upon Mr. Fradin's termination of employment with Aon. Mr. Fradin has agreed to retain at least until the end of 2011 (or earlier termination of employment) shares of Common Stock or securities exercisable for Common Stock with an aggregate value (using Black-Scholes methodology with regard to valuing stock options) of approximately $5 million and future equity grants (net of any taxes and exercise prices that are paid) until his departure from Aon. Mr. Fradin's equity awards are described in the Grants of Plan Based Awards in Fiscal Year 2010 table in this proxy statement.

        Each of the time-vested restricted stock units granted in connection with the ISP will vest ratably over a three-year period, and the time-vested restricted stock units granted to Mr. Fradin will vest in 25% equal installments on the second through fifth anniversaries of the grant date. Vesting of all such time-vested restricted stock units is contingent on Mr. Fradin's continued employment and other conditions as described in the section captioned "Potential Payments on Termination or Change-in-Control" contained in this proxy statement. The restricted stock units are settled in shares of Common Stock.

        With respect to restricted stock units awarded under the ISP, we provide dividend equivalents on unvested restricted stock units in cash at the time actual dividends on Aon's Common Stock are declared for stockholders. We do not provide dividend equivalents on performance-based equity awards.

Performance-Based Annual Bonus

        Shareholder-Approved Plan    For purposes of ensuring the deductibility of bonuses for our named executive officers, Aon's stockholders have approved a plan pursuant to which we award annual bonuses that meet the criteria under Section 162(m) of the Internal Revenue Code as "performance-based" compensation. That plan is called our Senior Officer Incentive Compensation Plan, as amended and restated in 2006 (the "Shareholder-Approved Plan"). Pursuant to this plan, the Compensation Committee annually sets an Aon-wide performance target (expressed in U.S. dollars) and minimum achievement threshold (expressed as a percentage). If the metric is not achieved, no bonuses are payable under the Shareholder-Approved Plan.

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        If the metric is achieved, the Shareholder-Approved Plan allows for the payment of deductible bonuses to our executive officers up to a cap. The cap is the lesser of $5 million or the maximum bonus otherwise established by the Compensation Committee for such executive officer. For 2010, the Compensation Committee established a cap of 300% of each named executive officer's target bonus, with the exception of Mr. Fradin, who did not participate in the Shareholder-Approved Plan for 2010.

        In the first quarter of 2010, the Compensation Committee set bonus eligibility for our named executive officers as a target percentage of the executive's base salary at year-end. The 2010 target bonus for Mr. McGill was subsequently increased from 150% to 175% of base salary pursuant to the employment agreement between Aon and Mr. McGill, dated December 7, 2010. The target bonuses and the applicable cap for each of our named executive officers are shown in the table below under the heading "Determination of 2010 Bonuses."

        The Shareholder-Approved Plan does not provide guidelines or formulas for determining the actual bonuses payable to our executive officers once the metric is achieved. Rather, the Compensation Committee retains sole discretion for determining the actual bonuses payable. If the metric is achieved, the Shareholder-Approved Plan would allow the Compensation Committee to award a bonus equal to the cap or allow it to exercise negative discretion to award a lesser amount. As explained below, for 2010 we adopted the "Executive Committee Incentive Plan" as a set of guidelines for consideration by the Compensation Committee in determining actual bonuses to be paid if the metric under the Shareholder-Approved Plan was achieved.

        2010 Metric Under Shareholder-Approved Plan    In the first quarter of 2010, the Compensation Committee determined that the 2010 Aon-wide performance target would be budgeted pre-tax income from continuing operations, excluding restructuring charges ("PTI") of $1,292 million. The Compensation Committee set the minimum achievement threshold at 85% of such target, or $1,098 million, as adjusted for extraordinary, unusual or infrequently occurring items. The Compensation Committee selected PTI as the measure to emphasize performance of Aon as a whole and directly link executives' awards to Aon's key business initiatives of delivering distinctive client value and achieving operational excellence. In combination with the performance targets established under each of LPP 3 through LPP 5 (i.e. cumulative EPS), we believe the targets balanced the executives' short and long-term perspective appropriately.

        The 2010 PTI target was set at a level higher than Aon's 2009 actual adjusted PTI. We also considered the past performance of our peer group in setting the target. We believed that the 2010 target was achievable but challenging. We set the minimum threshold at 85% because we believed performance below that level would not create sufficient value for our stockholders and, therefore, should not result in bonus payments.

        2010 Performance    During the first quarter of 2011, the Compensation Committee determined that Aon's 2010 PTI, after permitted adjustments for extraordinary or unusual items, was $1,250 million, or 96.7% of target. This exceeded the minimum threshold established under the Shareholder-Approved Plan.

        Executive Committee Incentive Plan    In the first quarter of 2010, the Compensation Committee approved a set of guidelines for funding the total bonus pool under the Shareholder-Approved Plan for the 14 executives that at such time comprised Aon's executive management committee or were senior executives regularly invited to attend meetings of such committee (collectively, the "executive management committee"). That group included each of the named executive officers other than Mr. Fradin. Mr. Appel was included in this group until his resignation from such committee effective

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November 5, 2010. The rationale for establishing funding guidelines was to provide executives with a clearer connection between the expected reward and the required performance, as well as for bonus accrual purposes.

        The funding formula was based on Aon's performance as measured by: (i) achievement of budgeted PTI; (ii) growth in PTI in 2010 as compared to 2009; and (iii) organic revenue growth. To align with the Shareholder-Approved Plan, the formula provided that no funding was to occur unless Aon achieved the minimum threshold of 85% of the 2010 PTI target. If that minimum threshold was achieved, the formula provided for adjustments to funding to account for year over year growth in PTI, 2010 organic revenue growth and other permissible adjustments. After consideration of each of these factors, the resulting bonus pool funding level is determined, and the funding level can range from 0% to 300%.

        The budgeted 2010 PTI growth rate was 3.6% over 2009 PTI. This was a slight increase as compared to the prior year's budgeted 2009 PTI growth rate of 3.1% over 2008 PTI. The incentive pool funding was determined by the aggregate of each executive management committee member's individual target bonus multiplied by a percentage varying from 0% to 300% depending on Aon's growth in PTI as compared to 2009. The plan provided that the funding level could be further increased up to 20% or reduced by 10% depending on Aon's 2010 organic revenue growth. The 2010 PTI growth over 2009 PTI was flat. In 2010, Aon experienced neither positive nor negative organic revenue growth.

        In the fourth quarter of 2010, on account of extraordinary market conditions Aon implemented a discretionary reduction to the funded pool of 10% and Aon's executive management committee voluntarily agreed to reduce the funded pool by an additional 10%, bringing the aggregate voluntary reduction to $2,776,600. In the first quarter of 2011, the Compensation Committee met to determine the funded status of the pool. While the Compensation Committee determined that the Executive Committee Incentive Plan missed the organic revenue growth target by 2/10ths of 1%, it approved the waiver of that reduction factor under the Executive Committee Incentive Plan, which resulted in additional funding of approximately $694,150. The Compensation Committee applied the remainder of the pre-established performance targets. After application of the PTI growth metric and the two discretionary reductions, and waiver of the organic revenue growth factor, the resulting bonus pool was determined to be funded at 103%. The bonus pool would have funded at 118% without application of the two discretionary reductions and waiver of the organic revenue growth factor.

        The actual size of the incentive pool equals the aggregate target bonuses multiplied by the percentage the pool was funded after application of the formula, as described above. For 2010, based on a funding level of 103%, the total incentive pool for members of the executive management committee was $14,299,490.

        Determination of 2010 Bonuses    Consistent with the Shareholder-Approved Plan, the bonus program for the executive management committee provides that the Compensation Committee has sole discretion to determine each executive's actual bonus amount as long as the corporate performance threshold was achieved. As explained above, for 2010 the threshold was achieved and, thus, the Compensation Committee had discretion to pay bonuses at the cap level or a lesser amount. It was anticipated that the Compensation Committee would consider in determining the executive's actual bonus, among other factors, the bonus for such executive at the pool funding level as well as the executive's targeted bonus allocation. However, the Compensation Committee reserved, and for 2010

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exercised, the discretion to set bonuses at levels higher or lower than the funded or targeted allocations.

        The Compensation Committee chose to exercise negative discretion with regard to each of the named executive officers. In other words, none of the named executive officers received their maximum bonus of the lesser of $5 million or 3 times their target bonus. In fact, each officer received in the range of 100%—133% of their target bonus. The following table sets forth the target bonus, cap, funded bonus, and actual bonus paid to each of our named executive officers, with the exception of Mr. Fradin who did not participate in the Executive Committee Incentive Plan:

        The Compensation Committee's rationale in determining the actual bonus awards was as follows:

•

In order for a named executive officer to get a bonus in excess of the funded bonus, there needed to be certain exceptional factors; however, the Compensation Committee did not utilize a formula for determining the amount of any named executive officer's bonus to be awarded greater or lesser than the funded or target bonus level.



•

With regard to Messrs. Case and McGill, the Compensation Committee determined it was appropriate to award a bonus at or near the named executive officer's target bonus level based on Aon's solid overall performance as reported.



•

With regard to Ms. Davies, the Compensation Committee determined it was appropriate to award a bonus greater than the funded level taking into consideration: (i) Aon's solid overall performance as reported; (ii) Ms. Davies' leading role in the acquisition of Hewitt during 2010; and (iii) Ms. Davies' continued success in significantly strengthening the global financial function and team.



•

With regard to Mr. O'Connor, the Compensation Committee determined it was appropriate to award a bonus greater than Mr. O'Connor's funded bonus level taking into consideration: (i) Aon's solid overall performance as reported; and (ii) the Compensation Committee's assessment that Mr. O'Connor was very successful in driving the continued improvement in the performance of our Risk Solutions business unit and in capturing and retaining cost savings in restructuring.



•

With regard to Mr. Dail, the Compensation Committee determined it was appropriate to award a bonus greater than Mr. Dail's funded bonus level taking into consideration: (i) Aon's solid overall performance as reported; and (ii) the Compensation Committee's assessment that Mr. Dail was highly effective on the Aon Hewitt transition team.

        For 2010, as was true in earlier years, generally all annual bonuses for executive officers are payable 65% in cash and 35% in restricted stock units, with such restricted stock units vesting ratably

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over a three-year period. The Compensation Committee believes this strikes a fair balance between reward for past performance and incentive for future improvements.

        Mr. Fradin's 2010 and 2011 Bonuses    As noted above, Mr. Fradin did not participate in the Executive Management Committee Incentive Plan during 2010; however, he will participate in this program in 2011 on the same terms as other participants. He participated in the incentive compensation program established at Hewitt through the end of Hewitt's fiscal year on September 30, 2010. The compensation committee of Hewitt's board of directors authorized a bonus payable to him for 2010 of $1,632,790. The bonus represented 137% of Mr. Fradin's target bonus and was calculated based on Hewitt's profit and revenue performance in 2010 prior to the Hewitt acquisition as well as the assessment by Hewitt's board of directors of other qualitative performance factors, including Mr. Fradin's leadership in the sale of Hewitt to Aon. Pursuant to Mr. Fradin's employment agreement with Aon, he is guaranteed a bonus of not less than $1,500,000 for fiscal 2011 year only.

        Mr. McGill's One-Time Transfer Payment    Pursuant to Mr. McGill's employment agreement, we provided him with a one-time transfer payment of $2,500,000. This payment is reflected in the "bonus" column of the Summary Compensation Table for Fiscal Years 2010, 2009 and 2008. The payment was made in recognition for his willingness to enter into the employment agreement having a five-year term, which resulted in the elimination of expatriate benefits, including housing allowance ($300,000 value per year) and forfeiture of participation in certain U.K. employee benefits (approximate value of $100,000 per year), including car allowance and pension contributions, and in recognition of Mr. McGill incurring relocation costs to permanently relocate to the U.S (approximate one-time cost of $500,000). If Mr. McGill voluntarily terminates his employment with Aon prior to November 18, 2015, he will be obligated to repay Aon a prorated portion of such transfer payment.

Other Policies and Practices

Internal Pay Fairness Considerations for Other Executive Officers

        In determining an executive officer's target bonus or long-term performance award value, the Compensation Committee will, from time to time, consider internal pay fairness factors. However, the Compensation Committee has not adopted a broad internal pay equity policy pursuant to which each executive officer's compensation, or one or more components thereof, is tied to or targeted against the compensation of other executive officers.

Base Salary

        Base salary is a fixed component of compensation and is initially set at a level based primarily upon the executive's job scope or level of responsibility. The base salaries of our senior-most executives are adjusted rarely, as our general practice is to increase other components of pay based upon superior performance. However, base salaries may be adjusted to, among other things, recognize a significant change in job function or responsibilities or to bring the fixed component of an executive's total compensation in line with his or her peers at Aon or the industry generally.

        We increased the base salaries of Ms. Davies and Mr. O'Connor to $800,000 from $750,000 and $700,000, respectively, effective March 1, 2010. Ms. Davies' and Mr. O'Connor's base salaries had not been increased since they joined Aon in 2007 and 2008, respectively. No base salary adjustments were made for any of our other named executive officers during 2010.

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Personal Benefits and Executive Benefits

Personal Benefits

        During 2010 we provided few personal benefits to our named executive officers as a component of their total compensation. Over the years, we have taken significant steps to de-emphasize personal benefits in our executive compensation practices.

Executive Benefits

        In addition to Aon's broad-based employee benefit programs that are available to Aon employees generally (such as health coverage, 401(k) salary deferrals, etc.), each of our named executive officers is eligible to participate in a deferred compensation program and a supplemental savings plan. In addition, Aon provides an executive health screening program available to all members of Aon's executive management committee, including the named executive officers. None of our named executive officers participate in our defined benefit pension plan or the supplemental pension program because each was hired after eligibility in the qualified plan was frozen in 2004. Additional information regarding certain of our executive benefits is set forth under the heading "Pension Benefits in Fiscal 2010" and the Nonqualified Deferred Compensation in Fiscal 2010 Table contained in this proxy statement.

Deferred Compensation Program

        We maintain a Deferred Compensation Plan (the "DCP") that allows certain employees, including our named executive officers, to defer receipt of their salary and/or annual incentive payments into Common Stock or accounts that mirror several different investment funds. Participants may defer up to 75% of salary and up to 100% of their annual bonus until the date(s) they have specified in accordance with the DCP's distribution provisions. Under the DCP we do not credit above-market interest on deferred compensation, as that term is defined in the Internal Revenue Code.

        Under the DCP, Aon does not make any contributions. We do not fund the DCP, and participants have an unsecured contractual commitment by Aon to pay the amounts due under the DCP. When such payments are due, the distributions will be made from our general assets. We have purchased corporate-owned life insurance to offset a portion of this liability.

U.S. Supplemental Savings Plan

        The Supplemental Savings Plan is a non-qualified, deferred compensation plan that provides eligible employees, including executives, with the opportunity to receive contributions that could not be credited under the Aon Savings Plan because of tax limitations and the specific provisions of such plan.

Post-Termination Compensation

        We believe that the provision of change-in-control severance agreements and other transitional compensation arrangements are critical to recruit talented employees and to secure the continued employment and dedication of our existing employees. All or nearly all of the companies with which we compete for talent have similar arrangements in place for their senior executives. While we consider these agreements to be necessary, the terms of these agreements are not considered as part of the compensation strategy when the Compensation Committee annually determines the compensation for the named executive officers. Additional information about post-termination compensation is set forth

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in the section captioned "Potential Payments on Termination or Change-in-Control" contained in this proxy statement.

Severance Agreements regarding Change-in-Control

        Beginning in 2005, we entered into change-in-control severance agreements with certain of our key executive officers, including each of our named executive officers. The agreements are intended to secure the continued service, and to ensure the dedication and objectivity of these executives in the event of an actual or threatened change-in-control of Aon. The agreements provide that covered executives receive certain severance benefits upon qualifying terminations of employment in connection with or within two years following a change-in-control of Aon. Thus, the agreements require a "double trigger"—a qualifying change-in-control of Aon and a qualifying termination of the executive's employment—in order for severance benefits to become payable.

        As adopted in 2005, the agreements also provided for excise tax gross-up protection in the event the executive becomes subject to tax under Section 280G of the Internal Revenue Code in connection with such double trigger. However, to better align with market practice, Aon has subsequently entered into with Mr. Case (in 2009) and Messrs. McGill and Fradin (in 2010) a form of change-in-control agreement that provides no excise tax gross-up protection in the event of a change-in-control of Aon. We intend to replace the 2005 form of agreement with the new version that is void of excise tax gross-up protection for our senior executives, including our named executive officers, who have change-in-control protection upon the executive's contract renewal or material contract amendment. While the new form of agreement generally is consistent with prevailing norms, the Compensation Committee believes the elimination of the excise tax gross-up protection can, and should, be made without jeopardizing the retentive value of the agreement. All newly-hired executives who are eligible for change-in-control protection will be required to enter in the new form of agreement.

        Mr. Fradin's change-in-control agreement provides for excise tax gross-up protection in connection with any parachute payment triggered by the Hewitt acquisition. This was a continuation, without modification, of the protection provided to Mr. Fradin under the change-in-control agreement he entered into with Hewitt.

        Additional information regarding the change-in-control agreement for our named executive officers is set forth in the section captioned "Potential Payments on Termination or Change-in-Control" contained in this proxy statement.

Employment Agreement with Mr. Fradin

        Mr. Fradin joined us in connection with the Hewitt acquisition on October 1, 2010. Aon entered into an employment agreement with Mr. Fradin on September 30, 2010, which is described in this proxy statement in the narrative section captioned "Employment Agreements and Other Compensation Arrangements" that follows the Grants of Plan-Based Awards in Fiscal Year 2010 table. In approving the agreement, the Compensation Committee considered Mr. Fradin's historical compensation with Hewitt, market practice, and the compensation and benefits customarily available to our executive officers. To provide significant incentive for Mr. Fradin's retention, and to ensure the performance-based nature of such incentive, the agreement committed Aon to provide Mr. Fradin with an additional award valued at $2 million under LPP 6 and an award valued at $2 million under the AHPP. In addition, the agreement provided for an award of time-vested restricted stock units to Mr. Fradin in connection with his retention by Aon following the Hewitt acquisition. Those restricted stock units were intended to incentivize Mr. Fradin to remain with Aon post-acquisition instead of terminating his

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employment relationship to collect change-in-control benefits to which he was otherwise entitled in connection with the acquisition.

Amendment of Mr. McGill's Employment Arrangement

        In the fourth quarter of 2010, we entered into an employment agreement with Mr. McGill, which modified and superseded the employment arrangement between Mr. McGill and our U.K. subsidiary, Aon Limited. Pursuant to the new agreement, Mr. McGill agreed to permanently relocate his residence to the U.S. and become directly employed by us. Mr. McGill's overseas assignment was scheduled to continue through January 1, 2013. However, due to his successful performance of the role of Chairman and Chief Executive Officer of Aon Risk Solutions and our desire to move him to our standard U.S. compensation and benefits programs we asked him to consider the permanent position and he agreed. The agreement is described in this proxy statement in the narrative section captioned "Employment Agreements and Other Compensation Arrangements" that follows the Grants of Plan-Based Awards in Fiscal Year 2010 table.

        The entry into the new agreement completed the steps we took with Mr. McGill during 2009 to level-set his compensation arrangement to that of our U.S.-based executive officers. During 2009, we amended Mr. McGill's employment arrangement as follows: (i) we fixed his base salary in U.S. dollars to alleviate the administrative burdens related to significant shifts in the foreign exchange rate between the U.S. and the U.K.; (ii) effective January 1, 2010, Mr. McGill was no longer eligible for a tax gross-up on his annual expatriate allowance and he was no longer eligible to participate in Aon's tax equalization policy for expatriates; and (iii) effective January 1, 2010, deferred pension amounts were no longer accrued for Mr. McGill.

Transition Agreement with Mr. Appel

        In the fourth quarter of 2010, we entered into a transition agreement with Mr. Appel. The agreement is described in this proxy statement in the narrative section captioned "Employment Agreements and Other Compensation Arrangements" that follows the Grants of Plan-Based Awards in Fiscal Year 2010 table. As a result of his termination, and pursuant to the transition agreement, Mr. Appel waived the right to receive change-in-control coverage under our standard change-in-control agreement. In approving the transition agreement with Mr. Appel, the Compensation Committee considered Aon's compensation and benefit obligations under Mr. Appel's employment agreement, Mr. Appel's overall contributions to Aon during his five years of service and conduct, and his commitment to transition his duties to other Aon executives over a brief period of time while remaining available thereafter for consultation on an as-needed basis.

Severance Benefits Pursuant to Employment Agreements

        We have entered into agreements with certain executive officers that provide for post-employment severance benefits and transitional compensation if the officer's employment terminates for a qualifying event or circumstance unrelated to a change-in-control of Aon, such as being terminated without "cause" as such term is defined in the operative agreement. Additional information regarding such post-employment severance or transitional compensation for Mr. Case and the other named executive officers is set forth in the section captioned "Potential Payments on Termination or Change-in-Control" contained in this proxy statement.

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Practices Regarding the Grant of Equity Awards

        We typically grant equity awards at regularly scheduled meetings of the Compensation Committee. Equity awards granted to Mr. Case are typically granted at regularly scheduled meetings of our Board of Directors by the independent members of the Board. During 2010, all equity awards granted to our named executive officers were awarded by the Compensation Committee (or, with regard to Mr. Case, the independent members of the Board) at regularly scheduled meetings or special meetings and valued at such dates. We do not have a policy or practice with respect to coordinating grant dates for equity awards with the release of material non-public information.

Recovery of Prior Performance-Based Equity Awards or Cash Bonuses

        We intend to adopt a recoupment policy providing for the adjustment or recovery of equity awards or cash payments if relevant Aon performance measures upon which such awards or payments were based are restated or otherwise adjusted in a manner that would have resulted in a reduced award or payment. Our policy will comply with the Dodd-Frank Wall Street Reform and Consumer Protection Act. We aim to adopt such policy as soon as practicable after the applicable implementing rules and regulations thereunder are issued. In the interim, the Compensation Committee will evaluate whether recovery or adjustment is appropriate based upon the facts and circumstances surrounding any restatement or adjustment.

Stock Ownership Guidelines

        In 2006, we adopted stock ownership guidelines, which have been revised from time to time including in September 2010, applicable to Aon's Chief Executive Officer, Chief Financial Officer and members of Aon's executive management committee. The guidelines are designed to increase executives' equity stakes in Aon and to align executives' interests more closely with those of our stockholders. The guidelines provide that the Chief Executive Officer should attain an investment position in Common Stock equal to six times annual base salary and each other executive officer, including the remainder of our named executive officers, should attain an investment position in Common Stock equal to three times annual base salary. These investment levels were immediately effective in 2010 for our CEO and will become effective January 1, 2012 for our other executive officers. The guidelines also set out equity retention rules generally requiring that net profit shares received upon the exercise of options to purchase Common Stock, the vesting of restricted stock units and the vesting of performance share units be retained until the required investment position is achieved. Shares of Common Stock counted toward these guidelines include: any shares owned outright; shares owned through an Aon-sponsored savings or retirement plan; shares purchased through an Aon-sponsored employee stock purchase plan; shares obtained through the exercise of stock options; shares issued upon the vesting of restricted stock units or performance share units; "phantom stock" held in the DCP; and "phantom stock" held in the Aon Supplemental Savings Plan.

Role of the Compensation Consultant

        The Compensation Committee has retained Frederic W. Cook & Co., Inc. as its independent executive compensation consultant. The role of the compensation consultant is described in this proxy statement under "Board of Directors and Committees—Organization and Compensation Committee—Relationship with Executive Compensation Consultant."

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Impact of Tax Treatment

        Section 162(m) of the Internal Revenue Code provides that a public corporation may take a deduction for compensation in excess of $1 million for its chief executive officer and certain of its other highest paid executive officers only if specific and detailed criteria are satisfied. Other sections of the Internal Revenue Code could result in adverse tax consequences to Aon and/or the executive related to certain change-in-control payments or the receipt of deferred compensation. Among other factors, we consider the company deductibility of compensation paid to the named executive officers.

        We recognize that the deductibility of some types of compensation payments can depend upon the timing of an executive's vesting or exercise of previously granted rights. The deductibility of compensation is also affected by interpretations of and changes in applicable tax laws and regulations as well as other factors beyond our control. Also, in some circumstances, factors other than tax deductibility are more important in determining the forms and levels of executive compensation most appropriate and in the best interests of Aon and its stockholders.

        For these and other reasons, we have determined that we will make a reasonable effort to administer Aon's compensation program in a tax-effective manner; however, we have from time to time approved elements of compensation for certain executive officers that are not fully deductible or result in adverse tax consequences to the executive and we reserve the right to do so in the future, when appropriate. For instance, we cannot deduct the portion of base salary in excess of $1 million that we paid to certain executive officers.

Historical Compensation of Executive Officers

        The executive compensation disclosure contained in this section reflects compensation information for the years ended December 31, 2010, December 31, 2009 and December 31, 2008. The following Summary Compensation Table for Fiscal Years 2010, 2009 and 2008 contains compensation information for: (1) Mr. Case, who served as our Chief Executive Officer during 2010; (2) Ms. Davies, who served as our Chief Financial Officer during 2010; (3) Messrs. Fradin, McGill, and O'Connor, who were our three other most highly compensated executive officers serving as of December 31, 2010; and (4) Mr. Dail, who served as co-Chief Executive Officer of Aon Consulting Worldwide, Inc. through the closing of Aon's acquisition of Hewitt on October 1, 2010, and Mr. Appel, who served as Aon's Chief Operating Officer through November 5, 2010, who would have been among our most highly compensated executive officers except that neither Mr. Dail nor Mr. Appel was serving as an executive officer as of December 31, 2010. We refer to these seven individuals in this proxy statement as our "named executive officers." No compensation information is provided for Mr. Fradin or Mr. O'Connor for 2008 or 2009 as they each became a named executive officer in 2010, and no compensation information is provided for Mr. Dail for 2008 as he became a named executive officer in 2009. In addition, the compensation information for Mr. Fradin reflects only compensation earned by Mr. Fradin during 2010 following the closing of the Hewitt acquisition on October 1, 2010.

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Summary Compensation Table for Fiscal Years 2010, 2009 and 2008

(1)

For purposes of this table, the amount set forth with respect to Mr. Fradin in column (c) for 2010 represents the salary paid to Mr. Fradin by Aon in 2010 following the closing of the Hewitt acquisition. For purposes of this table, the amounts set forth with respect to Mr. McGill in column (c) for all of 2008, and for a portion of 2009, have been converted from British pounds sterling to U.S. dollars based on the conversion rate in effect at the time of each of Mr. McGill's monthly salary payments. During 2009, Mr. McGill was paid in British pounds sterling through July 31, 2009 and in U.S. dollars for the remainder of 2009.

(2)

Except for Mr. McGill in 2010 and Ms. Davies in 2008, none of the named executive officers received any payments for 2010, 2009 or 2008 that would be characterized as "bonus" payments under the rules of the SEC. As the amount of the one-time transfer payment made to Mr. McGill in 2010 was guaranteed pursuant to his employment agreement, and the 2008 bonus paid to Ms. Davies was guaranteed pursuant to her employment agreement, each of these payments is reported in column (d) as a "bonus" payment. See the narrative section captioned "Employment Agreements and Other Compensation Arrangements" following the Grants of Plan-Based Awards in Fiscal Year 2010 table for more information on these agreements. Annual cash bonuses earned by the named executive officers in 2010, 2009 and 2008 as short-term incentive compensation are shown in column (g) "Non-Equity Incentive Plan Compensation."

(3)

The amounts shown in column (e) reflect the aggregate grant date fair value computed in accordance with FASB ASC Topic 718 for grants made in 2010, 2009 and 2008, respectively, of restricted stock unit awards and performance share unit awards granted to the named executive officers pursuant to the Stock Plan, and its sub-plans, specifically, the ISP, the LPP, the ABPP, and the AHPP, disregarding adjustments for forfeiture

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assumptions, and do not reflect amounts actually paid to, or realized by, the named executive officers in 2010, 2009 or 2008 or prior years. The ABPP was adopted during 2009 and, therefore, no grants under it are reflected in the table for 2008. The AHPP was adopted in March 2011, and Mr. Fradin's award thereunder was deemed granted in 2010. Of the named executive officers, only Messrs. Dail and Appel participate in the ABPP. Of the named executive officers, each of Mr. Fradin and Mr. Dail are eligible to participate in the AHPP; however, only Mr. Fradin received an award from Aon under the AHPP in 2010. Reflected in column (e) for each of 2010, 2009 and 2008 is the grant date fair value of the LPP grants and, if applicable, ABPP and AHPP grants, made on October 1, 2010 for the AHPP (for Mr. Fradin only), March 9, 2010 for the LPP, March 19, 2009 for the LPP (for each of the named executive officers other than Mr. Case), March 20, 2009 for the LPP (for Mr. Case only), April 22, 2009 for the ABPP (for Messrs. Appel and Dail only), and March 13, 2008 for the LPP, respectively, calculated in accordance with FASB ASC Topic 718 based on the probable outcome of the performance conditions at the time of grant with respect to performance share unit awards granted pursuant to the LPP, ABPP and AHPP, which is the dollar value attributed to the original share amount of the award multiplied by 100% for 2010, 100% for 2009 and 100% for 2008 for the LPP, 150% for 2009 for the ABPP, and 100% for the AHPP.

Set forth below are the grant date fair values of the performance share unit awards granted under the LPP, ABPP and AHPP, as applicable, calculated assuming: (i) the probable outcome of the performance conditions for each program as discussed in the prior paragraph, which amount is included in column (e) of this Summary Compensation Table; and (ii) achievement of the maximum levels of performance (which is the dollar value attributed to the original award multiplied by 200% for each of 2010, 2009 and 2008 for the LPP, 200% for 2009 for the ABPP, and 200% for 2010 for the AHPP).

The grant date fair value of the restricted stock units set forth in column (e) also reflects restricted stock units granted under the ISP in 2010, 2009 and 2008 as part of the annual incentive paid for service in 2009, 2008 and 2007, respectively, and: (i) for Mr. Fradin only, additional restricted stock unit awards granted to him in 2010 in connection with his commencement of employment with Aon upon the closing of the Hewitt acquisition; and (ii) for Mr. Appel only, additional restricted stock unit awards granted to him in 2009 in connection with an amendment to his employment agreement.

Assumptions used in the calculation of these amounts for each of 2010, 2009 and 2008 are set forth in Note 14 to Aon's audited financial statements for the year ended December 31, 2010 included in Aon's

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Annual Report on Form 10-K for the year ended December 31, 2010 filed with the SEC on February 25, 2011, which we refer to in this proxy statement as Aon's Annual Report on Form 10-K.

Mr. Appel's transition agreement outlines the treatment of the equity awards made to him in 2010 and earlier years. For further information about Mr. Appel's transition agreement, see the narrative section captioned "Employment Agreements and Other Compensation Arrangements" following the Grants of Plan-Based Awards in Fiscal Year 2010 table. As required by SEC rules, the amount shown in column (e) for 2010 for Mr. Appel includes the grant date fair value of all equity awards granted to Mr. Appel in 2010, including a performance share unit award granted to Mr. Appel in 2010 of which a portion will be forfeited.

The amounts shown in column (e) reflect the aggregate grant date fair value for these awards computed in accordance with FASB ASC Topic 718, and do not correspond to the actual value that will be recognized by the named executive officers. For further information on the stock awards granted in 2010, see the Grants of Plan-Based Awards in Fiscal Year 2010 table below.

(4)

The amounts shown in column (f) reflect the aggregate grant date fair value computed in accordance with FASB ASC Topic 718 for grants made in 2009 and 2008, respectively, of stock options pursuant to the Stock Plan and its sub-plan, the LPP, disregarding adjustments for forfeiture assumptions, and do not reflect amounts paid to, or realized by, the named executive officers in 2009 or 2008. No stock options were awarded to any of the named executive officers in 2010.

Assumptions used in the calculation of these amounts for each of 2009 and 2008 are set forth in Note 14 to Aon's audited financial statements for the year ended December 31, 2010 included in Aon's Annual Report on Form 10-K.

The amounts shown in column (f) reflect the aggregate grant date fair value computed in accordance with FASB ASC Topic 718, and do not correspond to the actual value that will be recognized by the named executive officers. Mr. Appel's transition agreement outlines the treatment of the equity awards made to him in 2010 and earlier years. For further information about Mr. Appel's transition agreement, see the narrative section captioned "Employment Agreements and Other Compensation Arrangements" following the Grants of Plan-Based Awards in Fiscal Year 2010 table.

(5)

With respect to the amounts set forth in column (g) for 2010: In the first quarter of 2011, the Compensation Committee granted the following awards under the Shareholder-Approved Plan based on the achievement of certain performance measures by the named executive officers during 2010: Mr. Case, $3,000,000; Ms. Davies, $1,600,000; Mr. Fradin, $1,632,790; Mr. McGill, $1,950,000; Mr. O'Connor, $1,000,000; and Mr. Dail, $1,000,000. In accordance with the terms of the ISP applicable to awards paid for 2010 service, all of the named executive officers receiving these awards other than Mr. Fradin were paid: (a) 65% of the awards in cash, and (b) 35% of the awards in the form of restricted stock units under the ISP. Mr. Fradin's award was paid entirely in cash. Pursuant to the terms of his transition agreement, Mr. Appel did not receive an award for 2010 service under the Shareholder-Approved Plan.

The amounts shown in column (g) for each of 2010, 2009 and 2008 reflect the cash portion of the awards paid to the named executive officers. The following amounts of restricted stock units represent the restricted stock unit portion of these awards granted with respect to 2010 performance: Mr. Case, 19,838; Ms. Davies, 10,786; Mr. McGill, 13,145; Mr. O'Connor, 6,741; and Mr. Dail, 6,741. To the extent these individuals are again designated as our named executive officers in future years, all of these restricted stock units will be shown in our Grants of Plan-Based Awards Table and our Outstanding Equity Awards at Fiscal Year-End Table and the applicable grant date fair value for these restricted stock units will be included in the amount in column (e) for 2011 compensation in future executive compensation disclosures that present information for the fiscal year ending December 31, 2011. For further information on the terms of the ISP, see the section captioned "Compensation Components and Analysis of 2010 Pay Decisions" in the Compensation Discussion and Analysis. For awards paid for service in 2009, the named executive officers that received such awards were paid 65% of the awards in cash and 35% in the form of restricted stock units under the ISP. For awards paid for service in 2008, the named executive officers that received such awards were paid 80% of the awards in cash and 20% in the form of restricted stock units under the ISP.

(6)

None of the named executive officers participates in a defined benefit plan. As a result, no amount is reported in column (h) for any named executive officer for changes in pension plan values. In addition, no

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amount is reported in column (h) for named executive officers for above market earnings on compensation that is deferred outside of tax qualified plans.

(7)

The amounts shown in column (i) for 2010 consist of the following components:

(a)

The amounts shown in the "Aon Contributions" column represent: (i) for each of the named executive officers other than Messrs. Fradin and McGill, a contribution by Aon of $14,700 to the Aon Savings Plan, a defined contribution plan; (ii) for each of the named executive officers other than Messrs. Fradin and McGill, a contribution to the Aon Supplemental Savings Plan, a non-qualified defined contribution plan in the following amounts: Mr. Case, $10,200; Ms. Davies, $7,650; Mr. O'Connor, $7,650; Mr. Dail, $10,200; and Mr. Appel, $10,200; (iii) for Mr. Fradin, a contribution by Aon of $13,015 to the Hewitt Associates Retirement and Savings Plan, and a defined contribution restoration allocation by Aon to the Hewitt Associates Voluntary Deferral Plan of $145,330, and (iv) for Mr. McGill, an unfunded contribution by Aon to Mr. McGill in connection with his pension entitlement as further described under "McGill Agreement" following the Nonqualified Deferred Compensation in 2010 table, converted from £45,000 (USD$73,188) based on the currency exchange rate in effect on January 15, 2010, the date on which the contribution was made. See the section captioned "Personal Benefits and Executive Benefits" in the Compensation Discussion and Analysis for additional information regarding these contributions and plans.



(b)

The amount shown in the "Other Compensation" column for Mr. McGill represents the portion of a $300,000 annual expatriate allowance paid to Mr. McGill in 2010 for payment of his costs associated with his expatriate assignment, including obtaining housing in Chicago, Illinois. In December 2010, in connection with Aon entering into a new employment arrangement with Mr. McGill, the expatriate allowance payable to Mr. McGill was eliminated. The expatriate allowance was previously paid to Mr. McGill pursuant to Aon's policy of providing coverage for duplicate costs incurred when employees are on a foreign assignment and retain a residence in their home countries. Mr. McGill's expatriate allowance was intended to cover actual costs incurred by Mr. McGill, who was a United Kingdom employee, of mortgage payments, property tax, insurance, maintenance and utility expenses on his Illinois residence. In addition, in prior years, Aon made tax payments to Mr. McGill related to his expatriate assignment to reduce double taxation. During 2010, Mr. McGill made payments to Aon of $196,444 in satisfaction of certain of these prior year tax amounts previously paid by Aon. This amount is not reflected in the table above as it was a payment from Mr. McGill to Aon. For further information on these payments to Mr. McGill see the sections captioned "Amendment of Mr. McGill's Employment Arrangement" in the Compensation Discussion and Analysis and "McGill Agreement" following the Nonqualified Deferred Compensation in Fiscal 2010 Table.


The amount shown in the "Other Compensation" column for Mr. Appel represents a lump sum payment to be made to Mr. Appel on May 5, 2011 pursuant to the terms of his transition agreement.

(c)

The amounts shown in the "Dividend Equivalents" column represent cash dividend equivalents paid on certain unvested restricted stock units granted under the ISP and, for Mr. Fradin, on a fully vested restricted stock unit award made in connection with the commencement of his employment.



(d)

The amounts shown in the "Perquisites" column represent:



(i)

for Mr. Case, the $2,150 value of his participation in our executive health screening program, which provides our executives the opportunity to obtain a comprehensive annual physical exam along with

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associated health benefits; and the $320 aggregate incremental cost incurred in connection with his spouse accompanying him on a business flight;

(ii)

for Mr. McGill, a $46,172 automobile allowance; and the $5,360 value of his participation in our executive health screening program;



(iii)

for Mr. O'Connor, the $5,400 value of his participation in our executive health screening program; and



(iv)

for Mr. Appel, the $4,630 value of his participation in our executive health screening program, and $17,500 paid for personal legal fees in connection with the negotiation of his transition agreement.

Aon has agreements in place with NetJets pursuant to which Aon pays hourly fees for its use of certain aircraft for business use. Spouses, families and invited guests occasionally accompany named executive officers on business-related flights. The cost to Aon of these additional guests is insubstantial.

(8)

Mr. Case also served as a Director of Aon in 2010, 2009 and 2008, but received no additional compensation for such service.

(9)

Ms. Davies joined Aon on November 12, 2007 as Executive Vice President, Global Finance and became Chief Financial Officer of Aon as of March 14, 2008.

(10)

Mr. Fradin joined Aon on October 1, 2010 as Chairman and Chief Executive Officer of Aon Hewitt upon the closing of the Hewitt acquisition.

(11)

Mr. McGill served as Chief Executive Officer of Aon Risk Services Americas during 2007 and through January 2008, and was named Chairman and Chief Executive Officer of Aon Risk Solutions in February 2008.

(12)

Mr. O'Connor joined Aon in February 2008 as Chief Operating Officer of Aon Risk Solutions.

(13)

Mr. Dail joined Aon in 2006 and has served Aon in several roles, including Co-Chief Executive Officer of Aon Consulting Worldwide, Inc. and Chief Operating Officer of Aon Benfield. Mr. Dail was an executive officer of Aon from April 2008 through November 2010. Mr. Dail currently serves as Chief Executive Officer—Global Consulting for Aon Hewitt.

(14)

Mr. Appel served as Chief Executive Officer of Aon Consulting Worldwide, Inc. during 2007 and through January 2008, was named Chief Executive Officer of Aon Re Global (which is now known as Aon Benfield) and Chairman of Aon Consulting Worldwide, Inc. in March 2008 and served in those capacities through April 2010, and was named Chief Operating Officer of Aon in April 2010. Pursuant to the terms of his transition agreement with Aon, Mr. Appel resigned as Aon's Chief Operating Officer on November 5, 2010 but continued as an employee of Aon through December 31, 2010. See the Grants of Plan-Based Awards in Fiscal Year 2010 and the Outstanding Equity Awards at 2010 Fiscal Year-End tables below and the description of Mr. Appel's transition agreement set forth in the narrative section captioned "Employment Agreements and Other Compensation Arrangements" following the Grants of Plan-Based Awards in Fiscal Year 2010 table for further information regarding the terms of Mr. Appel's transition, including the treatment of his equity awards.

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Grants of Plan-Based Awards in Fiscal Year 2010

        The following table provides information on non-equity incentive plan awards, stock options, restricted stock unit awards and performance share unit awards granted in 2010 to each of the named executive officers.

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        See the section captioned "How We Determine Total Compensation" in the Compensation Discussion and Analysis for information on the decision-making process with respect to the components of the total compensation of our named executive officers. In addition, the "Employment Agreements and Other Compensation Arrangements" section below provides additional information with respect to the named executive officers' compensation.

Employment Agreements and Other Compensation Arrangements

        Each of Mr. Case, Ms. Davies, and Messrs. Fradin, McGill, O'Connor and Dail has entered into an Employment Agreement with Aon. In addition, Mr. Appel is a party to a transition agreement with Aon. Each of the employment agreements and Mr. Appel's transition agreement addresses the payments and benefits these individuals will receive under various termination scenarios. These payments and benefits are described in the section entitled "Potential Payments on Termination or Change-in-Control" set forth in this proxy statement. Non-competition and non-solicitation covenants apply to each of the named executive officers for a period of two years, in each case following the termination of employment of such executive without regard to the reason for such termination.

        In addition to the employment agreements, each of Mr. Case, Ms. Davies, and Messrs. Fradin, McGill, O'Connor and Dail has entered into a severance agreement with Aon. Please see the section entitled "Potential Payments on Termination or Change-in-Control" of this proxy statement for a description of these agreements.

Mr. Case's Employment Agreement

        Aon has entered into an Amended and Restated Employment Agreement with Gregory C. Case, our President and Chief Executive Officer, dated November 13, 2009, which commenced November 13, 2009 and will expire April 3, 2015 unless terminated earlier. The agreement provides that Mr. Case will be employed as Aon's President and Chief Executive Officer. The agreement also provides that Mr. Case will be nominated for reelection as a member of Aon's Board of Directors at each annual meeting of stockholders during the period of his employment.

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        The agreement provides for an initial base salary of $1,500,000, subject to adjustment at the discretion of the Board of Directors, a target annual incentive bonus of not less than 200% of his base salary and an annual incentive bonus of up to 300% of the target annual incentive bonus, subject to the current cap of $5,000,000 established under the Shareholder-Approved Plan. The Board of Directors retains the discretion to determine Mr. Case's actual bonus payment.

        Pursuant to the agreement, subject to approval by the Board of Directors, Mr. Case received an additional award pursuant to Aon's LPP for the performance period beginning January 1, 2010 and ending December 31, 2012 with a grant date target value of $10,000,000. The $10,000,000 value was in addition to the value otherwise granted to Mr. Case pursuant to Aon's regular annual long-term incentive award process, and will be earned based on the same performance criteria and weightings as the regular annual long-term incentive award, which is also the same for other participants in Aon's LPP for the performance period. In addition, the agreement provides that Mr. Case will be provided with life insurance coverage in an amount no less than $5,000,000 during the term of the agreement.

Ms. Davies' Employment Agreement

        Aon has entered into an Employment Agreement with Christa Davies, our Executive Vice President, Global Finance and Chief Financial Officer, dated as of October 3, 2007, which will expire on November 11, 2012 unless terminated earlier. The agreement provides that Ms. Davies will be employed as Aon's Executive Vice President, Global Finance and effective March 14, 2008, Aon's Chief Financial Officer. The agreement provides for a base salary of no less than $750,000, subject to adjustment at the discretion of the Chief Executive Officer and the Compensation Committee of the Board of Directors, and a target annual incentive bonus of 150% of her base salary.

        Pursuant to the agreement, upon commencement of her employment, Ms. Davies received: (i) a restricted stock unit award of 85,000 shares of Common Stock, which vests in two installments of 33% of the shares on each of the third and fourth anniversaries of the date of grant; and one installment of 34% of the shares on the fifth anniversary of the date of grant; and (ii) a non-qualified stock option award to purchase 100,000 shares of Common Stock, which vests in two installments of 33% of the shares on each of the second and third anniversaries of the date of grant; and one installment of 34% on the fourth anniversary of the date of grant. In addition, upon commencement of her employment, Ms. Davies was paid a hiring bonus of $1,000,000, which was subject to repayment on a pro rata basis in the event Ms. Davies voluntarily terminated her employment with Aon prior to November 12, 2010.

Mr. Fradin's Employment Agreement

        Aon has entered into an Employment Agreement with Russell P. Fradin, our Chairman and Chief Executive Officer of Aon Hewitt, dated as of September 30, 2010, which commenced upon the closing of the Hewitt acquisition on October 1, 2010, and will expire October 1, 2015 unless terminated earlier. The agreement provides that Mr. Fradin will be employed as the Chairman and Chief Executive Officer of Aon Hewitt. The agreement provides for a base salary of no less than $1,000,000, subject to adjustment at the discretion of the Chief Executive Officer and the Compensation Committee of the Board of Directors, a target annual incentive bonus of not less than 150% of his base salary and a maximum annual incentive bonus of up to 450% of the target annual incentive bonus. The Board of Directors retains the discretion to determine Mr. Fradin's actual bonus payment.

        Pursuant to the agreement, upon commencement of his employment, Mr. Fradin received: (i) a fully vested restricted stock unit award of 127,291 shares of Common Stock, which shall be distributed to Mr. Fradin upon his departure from Aon; and (ii) a restricted stock unit award of 50,917 shares of

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Common Stock, which vests in four installments of 25% on each of the second, third, fourth and fifth anniversaries of the date of grant.

        In addition, pursuant to the agreement, Mr. Fradin received: (i) an award pursuant to Aon's LPP for the performance period beginning January 1, 2011 and ending December 31, 2013 with a fair market value of $2,000,000; and (ii) an award pursuant to the AHPP for the performance period beginning January 1, 2011 and ending December 31, 2013 with a fair market value of $2,000,000. Under the terms of the agreement, Mr. Fradin has agreed to hold until his departure from Aon: stock options originally exercisable for approximately 230,000 shares of Hewitt Associates that vested on October 1, 2010; restricted stock units of Hewitt Associates having an approximate aggregate value of $500,000 as of October 1, 2010; and future equity grants from Aon, net of any amounts used to pay the exercise price and taxes, if applicable.

Mr. McGill's Employment Agreement

        Aon entered into a Employment Agreement with Stephen P. McGill, our Chairman and Chief Executive Officer of Aon Risk Solutions, dated December 7, 2010, which commenced effective as of November 18, 2010 and will expire November 18, 2015, unless terminated earlier. The agreement modifies and supersedes the existing employment arrangement between Mr. McGill and Aon Limited, a United Kingdom subsidiary of Aon, dated April 22, 2005, as amended. The agreement provides that Mr. McGill will be employed as the Chairman and Chief Executive Officer of Aon Risk Solutions. The agreement provides for a base salary of no less than $1,100,000, subject to adjustment at the discretion of the Chief Executive Officer and the Compensation Committee of the Board of Directors, a target annual incentive bonus of 175% of his base salary for 2010 and 2011, and a maximum annual incentive bonus of up to 300% of the target annual incentive bonus, subject to the current cap of $5 million established under the Shareholder-Approved Plan. The Board of Directors retains the discretion to determine Mr. McGill's actual bonus payment.

        Pursuant to the agreement, Mr. McGill agreed to permanently relocate his residence to the United States from the United Kingdom, and become directly employed by Aon. Under the terms of the agreement, Mr. McGill received a one-time transfer payment of $2.5 million from Aon in recognition of his willingness to enter into the agreement, which resulted in the elimination of expatriate benefits previously received by Mr. McGill, including housing allowance, and the forfeiture by Mr. McGill of his participation in certain U.K. employee benefits, including car allowance and pension contributions, and incurring relocation costs to permanently relocate to the United States. If Mr. McGill voluntarily terminates his employment with Aon prior to November 18, 2015, he will be obligated to repay to Aon a prorated amount of such payment.

        Pursuant to the agreement, subject to the approval of the Compensation Committee of the Board of Directors, Mr. McGill received an additional award pursuant to Aon's LPP for the performance period beginning January 1, 2011 and ending December 31, 2013 with a grant date target value of $6 million. The $6 million value was in addition to the value to be otherwise granted to Mr. McGill pursuant to Aon's regular annual long-term incentive award process, and will be earned based on the same performance criteria and weightings as the regular annual long-term incentive award, which is also the same for other participants in Aon's LPP for the performance period.

Mr. O'Connor's Employment Agreement

        Aon has entered into an Employment Agreement with Michael J. O'Connor, our Chief Operating Officer of Aon Risk Solutions, dated as of February 25, 2008, which will expire on February 25, 2013

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unless terminated earlier. The agreement provides for a base salary of no less than $700,000, subject to adjustment, and a target annual incentive bonus of 100% of his base salary, subject to a cap of 300% of his base salary.

        Pursuant to the agreement, upon commencement of his employment, Mr. O'Connor received: (i) a restricted stock unit award of 50,000 shares of Common Stock, which vests in one installment of 34% on the third anniversary of the date of grant; and two installments of 33% on each of the fourth and fifth anniversaries of the date of grant; and (ii) a stock option award to purchase 50,000 shares of Common Stock, which vests in two installments of 33% of the shares on each of the second and third anniversaries of the date of grant; and one installment of 34% on the fourth anniversary of the date of grant.

        In addition, under the terms of the agreement, Mr. O'Connor received an award pursuant to Aon's LPP for the performance period beginning January 1, 2008 and ending December 31, 2010 with a grant date target value of $1,500,000.

Mr. Dail's Employment Agreement

        Aon has entered into an Employment Agreement with Baljit Dail, our Chief Executive Officer of Aon Hewitt Global Consulting, dated as of January 22, 2010, which will expire April 30, 2013 unless terminated earlier. The agreement provides for a base salary of no less than $800,000, subject to adjustment, and a target annual incentive bonus of 100% of his base salary, subject to a cap of 300% of his base salary. The agreement also provides that Mr. Dail will be eligible to participate in the long-term incentive compensation programs for Aon's senior executives.

Mr. Appel's Transition Agreement

        Aon has entered into a Transition Agreement with Andrew M. Appel, dated November 5, 2010, relating to Mr. Appel's resignation as Aon's Chief Operating Officer and his transition from Aon. In connection with the terms of the transition agreement, Aon and Mr. Appel agreed that Mr. Appel's employment would be terminated without cause effective as of December 31, 2010. In addition, pursuant to the transition agreement, effective November 5, 2010, Mr. Appel resigned his position as Aon's Chief Operating Officer, as an officer of any of its affiliates, and as a member of Aon's executive management committee.

        The transition agreement also provides that during the period beginning November 5, 2010 and ending on December 31, 2010, Mr. Appel will: (i) perform certain transitional duties as requested by Aon's Chief Executive Officer; and (ii) continue to participate in Aon's retirement and health care plans and programs on the same terms as other employees. Under the terms of the transition agreement, Mr. Appel waived entitlement to any bonus or other incentive compensation for which he otherwise may have been eligible for services performed during 2010.

        The transition agreement contains provisions that provide for the pro rata or continued vesting of certain stock options, restricted stock units, and performance share units pursuant to the terms and conditions of the plans and programs under which the awards were granted, including: (i) the satisfaction of the vesting requirements for the full fourth quarter of 2010 in connection with awards under various cycles of Aon's LPP and the ABPP; (ii) subsequent to December 31, 2010, continued vesting only in the restricted stock unit awards awarded to him from time to time pursuant to the ISP; and (iii) the forfeiture and cancellation as of December 31, 2010 of all other restricted stock units,

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performance share units and stock options previously granted to Mr. Appel by Aon during the course of his employment that will not vest by December 31, 2010.

        Aon has also agreed pursuant to the transition agreement to provide Mr. Appel with the following additional compensation and benefits: (i) a lump sum payment of $4,263,000, subject to applicable withholdings, on May 5, 2011; (ii) office and secretarial assistance through the earlier of the date he is re-employed elsewhere or September 30, 2011; (iii) provided Mr. Appel elects continuation health care coverage under COBRA, reimbursement for the difference between the premium rate he is required to pay and the active employee rate for similar coverage through September 30, 2011; (iv) reimbursement for up to $17,500 in reasonable legal fees and expenses incurred in connection with the negotiation and documentation of the transition agreement; and (v) standard executive-level outplacement assistance for the 2011 calendar year.

        The compensation and benefits payable to Mr. Appel under the transition agreement are subject to his executing and not revoking a release of claims. Aon has agreed to maintain a directors and officers liability insurance policy covering Mr. Appel to the extent it provides such coverage to its other executive officers or directors.

        For additional information regarding the Shareholder-Approved Plan and the LPP, see the section captioned "Compensation Components and Analysis of 2010 Pay Decisions" of the Compensation Discussion and Analysis.

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Outstanding Equity Awards at 2010 Fiscal Year-End

        The following table sets forth information regarding exercisable and unexercisable stock options, unvested restricted stock units and unvested performance share units held by each of the named executive officers on December 31, 2010. See "Potential Payments on Termination or Change-in-Control" for information regarding the impact of certain employment termination scenarios on outstanding equity awards.

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