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

                                    Form 13F

                              Form 13F COVER PAGE

Report for the Calendar Year or Quarter Ended:  March 31, 2002

Check here if Amendment [ ]; Amendment Number:
This Amendment (Check only one.):      [ ]  is a restatement.
                                       [ ]  adds new holdings entries.

Institutional Investment Manager Filing this Report:

Name:      Aon Advisors, Inc.
Address:   200 East Randolph Street
           Chicago, IL 60601

Name of additional disclosed party:

Name:      Aon Corporation
Address:   200 East Randolph Street
           Chicago, IL 60601

Form 13F File Number:  28-2005
                       28-2401

The institutional investment manager filing this report and the person by whom
it is signed hereby represent that the person signing the report is authorized
to submit it, that all information contained herein is true, correct and
complete, and that it is understood that all required items, statements,
schedules, lists, and tables, are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:

Name:   Michael A. Conway
Title:  President
Phone:  (312) 381-3330

Signature, Place, and Date of Signing:

/s/ Michael A. Conway             Chicago, IL                May 14, 2002
----------------------------      -----------------------    -----------------
[Signature]                       [City, State]              [Date]

Report Type (Check only one.):

[X] 13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager
    are reported in this report.)

[ ] 13F NOTICE. (Check here if no holdings reported are in this report, and
    all holdings are reported by other reporting manager(s).)

[ ] 13F COMBINATION REPORT. (Check here if a portion of the holdings for this
    reporting manager are reported in this report and a portion are reported by
    other reporting manager(s).)



                             Form 13F SUMMARY PAGE

Report Summary


Number of Other Included Managers:         0

Form 13F Information Table Entry Total:    179

Form 13F Information Table Value Total:    $432,709
                                           (thousands)

List of Other Included Managers


Provide a numbered list of the name(s) and Form 13F file number(s) of all
institutional investment managers with respect to which this report is filed,
other than the manager filing this report.

[If there are no entries in this list, state "NONE" and omit the column headings
and list entries]

    No.        Form 13F File Number       Name

    NONE






                                                   FORM 13F INFORMATION TABLE

          NAME OF ISSUER        TITLE OF CLASS               CUSIP     MARKET VALUE  PAR SHARES  ITEM:6  ITEM:7  ITEM:8
                                                                                            
ACM GOVT OPPOR FUND INC.        Common Stock                 000918102    39,991,917   4,655,636    X               X
AOL TIME WARNER                 Common Stock                 00184A105     4,637,316     196,081    X               X
AT&T CORP.                      Common Stock                 001957109       157,022      10,001    X               X
AT&T WIRELESS SERVICES          Common Stock                 00209A106       549,136      61,356    X               X
ABBOTT LABORATORIES             Common Stock                 002824100     1,578,000      30,000    X               X
ALCOA, INC.                     Common Stock                 013817101     2,264,400      60,000    X               X
ALLIED WASTE INDUSTRIES INC     Common Stock                 019589308     1,495,234     115,018    X               X
ALLTEL CORP.                    Common Stock                 020039103     2,499,750      45,000    X               X
AMERICAN INTERNATIONAL GROUP    Common Stock                 026874107     8,682,843     120,361    X               X
AMGEN, INC.                     Common Stock                 031162100     3,031,744      50,800    X               X
ANDREW CORPORATION              Common Stock                 034425108     1,422,050      85,000    X               X
ANHEUSER-BUSCH COMPANIES INC    Common Stock                 035229103     3,915,000      75,000    X               X
AON FUNDS                       Common Stock                 036912889    79,849,467   7,969,009    X               X
APACHE CORP.                    Common Stock                 037411105     1,001,088      17,600    X               X
BP AMOCO PLC                    Common Stock                 055622104     3,345,300      63,000    X               X
BIOGEN                          Common Stock                 090597105     1,373,680      28,000    X               X
BOLDER TECHNOLOGIES CORP.       Common Stock                 097519102            61      76,595    X               X
BRISTOL MYERS SQUIBB            Common Stock                 110122108     2,348,420      58,000    X               X
BURLINGTON NORTHERN/SANTA FE    Common Stock                 12189T104     1,418,460      47,000    X               X
CSX CORPORATION                 Common Stock                 126408103     2,667,700      70,000    X               X
CVS CORPORATION                 Common Stock                 126650100     1,373,200      40,000    X               X
CARDINAL HEALTH INC.            Common Stock                 14149Y108     4,076,175      57,500    X               X
CARNIVAL CORP                   Common Stock                 143658102     1,959,000      60,000    X               X
CHEVRONTEXACO CORP              Common Stock                 166764100     3,520,530      39,000    X               X
CISCO SYSTEMS                   Common Stock                 17275R102     1,083,520      64,000    X               X
CITIGROUP INC.                  Common Stock                 172967101     5,304,236     107,113    X               X
CITRIX SYSTEMS INC              Common Stock                 177376100       864,000      50,000    X               X
CLEAR CHANNEL COMM              Common Stock                 184502102     4,338,644      84,393    X               X
COCA COLA CO                    Common Stock                 191216100     3,396,900      65,000    X               X
COLGATE PALMOLIVE CO            Common Stock                 194162103     2,360,295      41,300    X               X
COMPAQ COMPUTER                 Common Stock                 204493100       313,500      30,000    X               X
COMVERSE TECHNOLOGY,INC         Common Stock                 205862402       443,450      35,000    X               X
CONCORD EFS INC                 Common Stock                 206197105       997,500      30,000    X               X
CONSECO CONVERTIBLE SEC. FUND   Common Stock                 20846T672       981,041     103,159    X               X
CORNING INC.                    Common Stock                 219350105       419,100      55,000    X               X
DRS TECHNOLOGIES, INC.          Common Stock                 23330X100        41,450       1,000    X               X
DEAN FOODS                      Common Stock                 242370104       990,720      13,084    X               X
DEERE & CO                      Common Stock                 244199105     2,186,400      48,000    X               X
DELL COMPUTER CORP              Common Stock                 247025109     2,916,487     111,700    X               X
DELUXE CORP                     Common Stock                 248019101       855,810      18,500    X               X
DEVON ENERGY                    Common Stock                 25179M103     2,413,500      50,000    X               X
DIGITAL RIVER INC               Common Stock                 25388B104       444,300      30,000    X               X
THE WALT DISNEY CO.             Common Stock                 254687106     2,308,000     100,000    X               X
DIVINE INTERVENTURES            Common Stock                 255402109       833,335   1,666,669    X               X
DOW CHEMICAL                    Common Stock                 260543103     1,734,160      53,000    X               X
DUKE REALTY CORP.               Common Stock                 264411505       390,003      15,000    X               X
EMC CORP./MASS                  Common Stock                 268648102       655,600      55,000    X               X
EASTMAN CHEMICAL                Common Stock                 277432100     3,171,350      65,000    X               X
EMERSON ELECTRIC CO.            Common Stock                 291011104     2,754,720      48,000    X               X
ENGINEERED SUPPORT SYSTEMS INC  Common Stock                 292866100       555,000      12,000    X               X
EQUITY OFFICE PROPERTIES TRUST  Common Stock                 294741103       581,009      19,373    X               X
EXXON MOBIL CORP                Common Stock                 30231G102     5,040,713     115,006    X               X
FEDERAL HOME LOAN MTGE CORP     Common Stock                 313400301     1,001,246      15,800    X               X
FEDERAL NATIONAL MORTGAGE ASSN  Common Stock                 313586109     5,807,276      72,700    X               X
FIBERMARK INC                   Common Stock                 315646109       197,835      32,700    X               X
FIRST DATA CORPORATION          Common Stock                 319963104     1,804,068      20,677    X               X
FIRST FEDERAL SAVINGS BANK      Common Stock                 33761K105       206,955       7,161    X               X
FORD MOTOR COMPANY              Common Stock                 345370860     3,628,822     220,062    X               X
FOUNDRY NETWORKS IN             Common Stock                 35063R100       100,660      14,000    X               X
FOX ENTERTAINMENT GRP INC-A     Common Stock                 35138T107       520,300      22,000    X               X
GENERAL ELECTRIC                Common Stock                 369604103     7,045,693     188,136    X               X
GENTEX CORP                     Common Stock                 371901109       592,600      20,000    X               X
GENZYME CORP.                   Common Stock                 372917104       869,033      19,900    X               X
GEORGIA-PACIFIC CORP            Common Stock                 373298108     2,006,650      67,000    X               X
GIBRALTAR STEEL CO.             Common Stock                 37476F103       130,560       6,000    X               X
W.W. GRAINGER INC.              Common Stock                 384802104     2,249,200      40,000    X               X
HCA INC                         Common Stock                 404119109     1,763,200      40,000    X               X
HRPT PROPERTIES, INC            Common Stock                 40426W101     1,820,700     202,300    X               X
JOHN HANCOCK FINANCIAL SVCS     Common Stock                 41014S106       146,993       3,849    X               X
HARTMARX                        Common Stock                 417119104       212,310     101,100    X               X
HELMERICH AND PAYNE INC.        Common Stock                 423452101       408,918      10,200    X               X
HEWLETT PACKARD CO.             Common Stock                 428236103     1,309,620      73,000    X               X
HOME DEPOT INC                  Common Stock                 437076102     3,551,495      73,061    X               X
HONEYWELL INTERNATIONAL INC.    Common Stock                 438516106     1,856,095      48,500    X               X
ILLINOIS TOOL WORKS INC.        Common Stock                 452308109     2,894,000      40,000    X               X
INTEL CORPORATION               Common Stock                 458140100     2,615,260      86,000    X               X
INT'L BUSINESS MACHINES         Common Stock                 459200101     5,616,000      54,000    X               X
INTERNATIONAL PAPER COMPANY     Common Stock                 460146103       903,210      21,000    X               X
JOHNSON & JOHNSON               Common Stock                 478160104     7,828,553     120,532    X               X
KELLOGG CO.                     Common Stock                 487836108     1,074,240      32,000    X               X
KROGER                          Common Stock                 501044101     2,091,195      94,368    X               X
L-3 COMMUNICATIONS HLDGS INC    Common Stock                 502424104     3,270,400      29,200    X               X
LIBERTY MEDIA CORP-A            Common Stock                 530718105       758,400      60,000    X               X
ELI LILLY & CO.                 Common Stock                 532457108     2,667,000      35,000    X               X
LITTELFUSE, INC.                Common Stock                 537008104       990,800      40,000    X               X
MGIC INVESTMENT CORP            Common Stock                 552848103     1,710,750      25,000    X               X
MAY DEPT STORES                 Common Stock                 577778103     2,195,550      63,000    X               X
MCDONALDS CORP                  Common Stock                 580135101     1,110,000      40,000    X               X
MEDIMMUNE INC                   Common Stock                 584699102     1,573,200      40,000    X               X
MERCK & CO.                     Common Stock                 589331107     2,879,000      50,000    X               X
MICROSOFT CORP.                 Common Stock                 594918104     5,638,985      93,500    X               X
MOBILE MINI INC                 Common Stock                 60740F105     1,837,478      57,100    X               X
MORGAN STANLEY DEAN WITTER & C  Common Stock                 617446448     2,177,814      38,001    X               X
NANOPHASE TECHNOLOGIES          Common Stock                 630079101       480,318      57,800    X               X
NASDAQ 100 SHARES               Common Stock                 631100104     2,188,590      60,693    X               X
NEWPARK RESOURCES INC.          Common Stock                 651718504       966,301     124,684    X               X
NEWS CORP LTD-SPONS ADR         Common Stock                 652487703       823,020      29,000    X               X
NOKIA ADR A                     Common Stock                 654902204     1,845,860      89,000    X               X
NORFOLK SOUTHERN CORP           Common Stock                 655844108     2,506,518     104,700    X               X
NORTHROP GRUMMAN CORP           Common Stock                 666807102       487,901       4,316    X               X
NORTHSTAR CAPITAL INVMNT GRP    Common Stock                 66704F106     4,947,500     250,000    X               X
NORTHSTAR CAPITAL INVMNT GRP    Common Stock                 66704F999     1,061,120      53,619    X               X
NUCOR CORP                      Common Stock                 670346105     1,413,280      22,000    X               X
OMEGA WORLDWIDE INC             Common Stock                 68210B108        41,996      19,998    X               X
PEPSICO INC                     Common Stock                 713448108     1,287,500      25,000    X               X
PETROLEUM GEO-SVCS -SPON ADR    Common Stock                 716597109       618,450      95,000    X               X
PFIZER, INC.                    Common Stock                 717081103     6,537,230     164,500    X               X
PITNEY BOWES INC                Common Stock                 724479100     1,112,800      26,000    X               X
BANCO POPULAR                   Common Stock                 733174106        77,160       2,641    X               X
POWERWAVE TECHNOLOGIES INC      Common Stock                 739363109     1,171,170      91,000    X               X
PRICE LEGACY CORPORATION        Common Stock                 74144P106       142,938      44,668    X               X
PRUDENTIAL FINANCIAL INC.       Common Stock                 744320102        78,091       2,515    X               X
PUBLIC STORAGE INC.             Common Stock                 74460D109            26           1    X               X
QUANTA SERVICES INC             Common Stock                 74762E102     1,158,430      67,000    X               X
RADIANT SYSTEMS INC             Common Stock                 75025N102       343,900      38,000    X               X
RADIOSHACK CORP                 Common Stock                 750438103     1,051,400      35,000    X               X
RIO ALTO EXPLORATION LTD        Common Stock                 766892103       775,941      80,000    X               X
ROYAL DUTCH PETROLEUM CO.       Common Stock                 780257804       325,920       6,000    X               X
SPX CORPORATION                 Common Stock                 784635104     2,548,440      18,000    X               X
SSGA CORP BOND INDEX FUND       Common Stock                 78899H920    13,094,466     957,968    X               X
SAKS INCORPORATED               Common Stock                 79377W108       631,200      48,000    X               X
SANDISK CORP                    Common Stock                 80004C101       499,100      23,000    X               X
SCHERING PLOUGH CORP            Common Stock                 806605101     3,969,090     126,808    X               X
SCHOLASTIC CORP                 Common Stock                 807066105     2,709,500      50,000    X               X
SHELL TRANSPORT - TRADING ADR   Common Stock                 822703609       885,600      20,000    X               X
SHIRE PHARMACEUTICALS           Common Stock                 82481R106       516,362      22,000    X               X
SIX FLAGS INC.                  Common Stock                 83001P109     1,250,200      70,000    X               X
SPRINT CORPORATION              Common Stock                 852061506       391,020      38,000    X               X
STATE STREET CORP               Common Stock                 857477103     1,661,400      30,000    X               X
SUN MICROSYSTEMS, INC.          Common Stock                 866810104     1,137,780     129,000    X               X
SUNGARD DATA SYSTEMS            Common Stock                 867363103     2,637,600      80,000    X               X
SYMANTEC CORP                   Common Stock                 871503108     1,648,400      40,000    X               X
TARGET CORP                     Common Stock                 87612E106     2,156,000      50,000    X               X
TECHNITROL INC                  Common Stock                 878555101       953,600      40,000    X               X
TELLABS INC.                    Common Stock                 879664100     1,094,115     104,500    X               X
TENET HEALTHCARE CORP           Common Stock                 88033G100     3,015,900      45,000    X               X
TEXAS INSTRUMENTS               Common Stock                 882508104     1,026,100      31,000    X               X
TEXTRON, INC                    Common Stock                 883203101     2,197,300      43,000    X               X
TRIBUNE CO                      Common Stock                 896047107     4,273,240      94,000    X               X
TROPICAL SPORTSWEAR INTL        Common Stock                 89708P102       396,000      16,500    X               X
U.S. AIRWAYS GROUP, INC.        Common Stock                 911905107       126,381      19,594    X               X
VF CORP.                        Common Stock                 918204108     1,513,750      35,000    X               X
VERIZON CORPORATION             Common Stock                 92343V104     1,613,500      35,000    X               X
VIACOM INC                      Common Stock                 925524100     1,458,000      30,000    X               X
VIACOM INC                      Common Stock                 925524308       572,701      11,840    X               X
WACHOVIA CORP. 2ND NEW COM      Common Stock                 929903102     2,781,000      75,000    X               X
WAL-MART STORES, INC.           Common Stock                 931142103     1,103,400      18,000    X               X
WALGREENS CO                    Common Stock                 931422109     4,604,825     117,500    X               X
WATSCO                          Common Stock                 942622101       216,000      12,000    X               X
WATSCO                          Common Stock                 942622200     1,088,850      61,000    X               X
WINTRUST FINANCIAL CORP         Common Stock                 97650W108     1,609,049      70,050    X               X
WIRELESS TELECOM GROUP, INC.    Common Stock                 976524108       355,104     109,600    X               X
WORLDCOM INC                    Common Stock                 98157D106       900,464     133,600    X               X
WORLDCOM INC                    Common Stock                 98157D304         9,834       1,664    X               X
WRIGLEY, (WM) JR. CO.           Common Stock                 982526105     1,226,130      23,000    X               X
WYETH                           Common Stock                 983024100       787,800      12,000    X               X
YAHOO ! INC.                    Common Stock                 984332106     1,394,901      75,523    X               X
YOUNG BROADCASTING CORP -A      Common Stock                 987434107     1,636,845      65,500    X               X
ZIMMER HOLDINGS INC             Common Stock                 98956P102     1,021,500      30,000    X               X
MAX RE CAPITAL LTD.             Common Stock                 G6052F103            10           1    X               X
TRENWICK GROUP                  Common Stock                 G9032C109     5,204,385     580,199    X               X
AUDIOCODES LTD                  Common Stock                 M15342104       170,000      50,000    X               X
SUN INTERNATIONAL HOTELS LTD-A  Common Stock                 P8797T133       326,520      12,000    X               X
CKE RESTAURANTS INC             Taxable Bonds-Convertible    12561EAB1       974,550   1,095,000    X               X
CLEAR CHANNEL COMM              Taxable Bonds-Convertible    184502AE2       410,656     425,000    X               X
ESC MEDICAL SYSTEMS             Taxable Bonds-Convertible    269025AA0       511,619     545,000    X               X
ESC MEDICAL SYSTEMS             Taxable Bonds-Convertible    269025AB8       300,400     320,000    X               X
GETTY IMAGES, INC               Taxable Bonds-Convertible    374276AD5     2,655,000   3,000,000    X               X
GOLD EAGLE CAPITAL 2001         Taxable Bonds-Convertible    38058MAA0     4,001,320   4,000,000    X               X
HILTON HOTELS CORP.             Taxable Bonds-Convertible    432848AL3       639,563     675,000    X               X
INTERIM SERVICES, INC.          Taxable Bonds-Convertible    45868PAA8       929,425   1,130,000    X               X
MASCOTECH INC.                  Taxable Bonds-Convertible    574670AB1       358,000     400,000    X               X
MUTUAL RISK                     Taxable Bonds-Convertible    628351AA6       195,000   1,000,000    X               X
QUANTA SERVICES INC             Taxable Bonds-Convertible    74762EAA0     1,407,500   2,000,000    X               X
THERMO INSTRUMENT SYSTEMS       Taxable Bonds-Convertible    883559AE6       648,956     695,000    X               X
THERMO FIBERTEK INC             Taxable Bonds-Convertible    88355WAA3       472,500     500,000    X               X
THERMO FIBERTEK INC             Taxable Bonds-Convertible    VV3081948       500,000     500,000    X               X
BOLDER TECHNOLOGIES CORP.       Preferred Stock-Convertible  097519201           800      40,000    X               X
FLEET BOSTON FINANCIAL CORP     Preferred Stock-Convertible  339030702       253,193       4,950    X               X

                                                                         432,709,503  40,911,032