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

                                    Form 13F

                              Form 13F COVER PAGE

Report for the Calendar Year or Quarter Ended:  June 30, 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                August 8, 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:    150

Form 13F Information Table Value Total:    $289,206
                                           (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    41,342,051   4,655,636    X               X
AOL TIME WARNER                 Common Stock                 00184A105     2,884,352     196,081    X               X
AT&T WIRELESS SERVICES          Common Stock                 00209A106       358,933      61,356    X               X
ABBOTT LABORATORIES             Common Stock                 002824100     1,129,500      30,000    X               X
ALCOA, INC.                     Common Stock                 013817101     1,989,000      60,000    X               X
ALLIED WASTE INDUSTRIES INC     Common Stock                 019589308     1,104,173     115,018    X               X
ALLTEL CORP.                    Common Stock                 020039103     2,115,000      45,000    X               X
AMERICAN INTERNATIONAL GROUP    Common Stock                 026874107     8,212,231     120,361    X               X
AMGEN, INC.                     Common Stock                 031162100     2,127,504      50,800    X               X
ANADARKO PETROLEUM CORP         Common Stock                 032511107     1,873,400      38,000    X               X
ANDREW CORPORATION              Common Stock                 034425108     1,268,200      85,000    X               X
ANHEUSER-BUSCH COMPANIES INC    Common Stock                 035229103     3,750,000      75,000    X               X
APACHE CORP.                    Common Stock                 037411105     3,178,644      55,300    X               X
AVERY DENNISON CORP             Common Stock                 053611109       665,150      10,600    X               X
BP AMOCO PLC                    Common Stock                 055622104     3,180,870      63,000    X               X
BIOGEN                          Common Stock                 090597105     1,160,040      28,000    X               X
BRISTOL MYERS SQUIBB            Common Stock                 110122108     1,490,600      58,000    X               X
BURLINGTON NORTHERN/SANTA FE    Common Stock                 12189T104     1,410,000      47,000    X               X
CSX CORPORATION                 Common Stock                 126408103     2,453,500      70,000    X               X
CVS CORPORATION                 Common Stock                 126650100     1,224,000      40,000    X               X
CARDINAL HEALTH INC.            Common Stock                 14149Y108     3,531,075      57,500    X               X
CARNIVAL CORP                   Common Stock                 143658102     1,661,400      60,000    X               X
CHEVRON TEXACO CORP.            Common Stock                 166764100     3,451,500      39,000    X               X
CISCO SYSTEMS                   Common Stock                 17275R102       892,800      64,000    X               X
CITIGROUP, INC.                 Common Stock                 172967101     4,150,629     107,113    X               X
CITRIX SYSTEMS INC              Common Stock                 177376100       302,000      50,000    X               X
CLEAR CHANNEL COMM              Common Stock                 184502102     2,702,264      84,393    X               X
COCA COLA CO                    Common Stock                 191216100     3,052,000      54,500    X               X
COLGATE PALMOLIVE CO            Common Stock                 194162103     2,402,400      48,000    X               X
COMVERSE TECHNOLOGY,INC         Common Stock                 205862402       324,100      35,000    X               X
CONCORD EFS INC                 Common Stock                 206197105       904,200      30,000    X               X
CORNING INC.                    Common Stock                 219350105       195,250      55,000    X               X
DEAN FOODS                      Common Stock                 242370104       976,066      26,168    X               X
DEERE & CO                      Common Stock                 244199105     2,299,200      48,000    X               X
DELL COMPUTER CORP              Common Stock                 247025109     2,919,838     111,700    X               X
DELUXE CORP                     Common Stock                 248019101       921,693      23,700    X               X
DEVON ENERGY                    Common Stock                 25179M103     2,464,000      50,000    X               X
DIGITAL RIVER INC               Common Stock                 25388B104       275,700      30,000    X               X
THE WALT DISNEY CO.             Common Stock                 254687106     1,890,000     100,000    X               X
DIVINE INTERVENTURES            Common Stock                 255402406        86,666      22,222    X               X
DOW CHEMICAL                    Common Stock                 260543103     1,822,140      53,000    X               X
DUKE REALTY CORP.               Common Stock                 264411505       434,253      15,000    X               X
EMC CORP./MASS                  Common Stock                 268648102       415,250      55,000    X               X
EASTMAN CHEMICAL                Common Stock                 277432100     3,048,500      65,000    X               X
EMERSON ELECTRIC CO.            Common Stock                 291011104     2,568,480      48,000    X               X
ENGINEERED SUPPORT SYSTEMS INC  Common Stock                 292866100       543,920      10,400    X               X
EQUITY OFFICE PROPERTIES TRUST  Common Stock                 294741103     1,224,271      40,673    X               X
EXXON MOBIL CORP                Common Stock                 30231G102     6,621,102     161,806    X               X
FEDERAL HOME LOAN MTGE CORP     Common Stock                 313400301       966,960      15,800    X               X
FEDERAL NATIONAL MORTGAGE ASSN  Common Stock                 313586109     5,361,625      72,700    X               X
FIBERMARK INC                   Common Stock                 315646109       277,950      32,700    X               X
FIRST DATA CORPORATION          Common Stock                 319963104       769,184      20,677    X               X
FORD MOTOR COMPANY              Common Stock                 345370860     3,520,992     220,062    X               X
FOUNDRY NETWORKS IN             Common Stock                 35063R100        98,420      14,000    X               X
FOX ENTERTAINMENT GRP INC-A     Common Stock                 35138T107       478,500      22,000    X               X
GENERAL ELECTRIC                Common Stock                 369604103     5,465,351     188,136    X               X
GENTEX CORP                     Common Stock                 371901109       549,400      20,000    X               X
GENZYME CORP.                   Common Stock                 372917104       546,416      28,400    X               X
GEORGIA-PACIFIC CORP            Common Stock                 373298108     1,646,860      67,000    X               X
W.W. GRAINGER INC.              Common Stock                 384802104     2,004,000      40,000    X               X
HCA INC                         Common Stock                 404119109     1,900,000      40,000    X               X
HRPT PROPERTIES, INC            Common Stock                 40426W101     1,790,355     202,300    X               X
HARTMARX                        Common Stock                 417119104       252,750     101,100    X               X
HELMERICH AND PAYNE INC.        Common Stock                 423452101       364,344      10,200    X               X
HEWLETT PACKARD CO.             Common Stock                 428236103     1,405,378      91,975    X               X
HOME DEPOT INC                  Common Stock                 437076102     3,197,751      87,061    X               X
HONEYWELL INTERNATIONAL INC.    Common Stock                 438516106     1,708,655      48,500    X               X
ILLINOIS TOOL WORKS INC.        Common Stock                 452308109     2,732,000      40,000    X               X
INTEL CORPORATION               Common Stock                 458140100     1,571,220      86,000    X               X
INT'L BUSINESS MACHINES         Common Stock                 459200101     3,888,000      54,000    X               X
INTERNATIONAL PAPER COMPANY     Common Stock                 460146103       915,180      21,000    X               X
JOHNSON & JOHNSON               Common Stock                 478160104     6,299,002     120,532    X               X
KROGER                          Common Stock                 501044101     1,877,923      94,368    X               X
L-3 COMMUNICATIONS HLDGS INC    Common Stock                 502424104     1,576,800      29,200    X               X
LIBERTY MEDIA CORP-A            Common Stock                 530718105       600,000      60,000    X               X
ELI LILLY & CO.                 Common Stock                 532457108     1,974,000      35,000    X               X
LITTELFUSE, INC.                Common Stock                 537008104       925,200      40,000    X               X
MGIC INVESTMENT CORP            Common Stock                 552848103       847,500      12,500    X               X
MAY DEPT STORES                 Common Stock                 577778103     2,074,590      63,000    X               X
MCDONALDS CORP                  Common Stock                 580135101     1,138,000      40,000    X               X
MEDIMMUNE INC                   Common Stock                 584699102     1,056,000      40,000    X               X
MERCK & CO.                     Common Stock                 589331107     2,532,000      50,000    X               X
MERRILL LYNCH & CO.             Common Stock                 590188108     1,215,000      30,000    X               X
MICROSOFT CORP.                 Common Stock                 594918104     5,114,450      93,500    X               X
MOBILE MINI INC                 Common Stock                 60740F105       976,410      57,100    X               X
MORGAN STANLEY DEAN WITTER & C  Common Stock                 617446448     1,637,040      38,000    X               X
NANOPHASE TECHNOLOGIES          Common Stock                 630079101       338,130      57,800    X               X
NASDAQ 100 SHARES               Common Stock                 631100104     1,584,087      60,693    X               X
NEWPARK RESOURCES INC.          Common Stock                 651718504       916,427     124,684    X               X
NEWS CORP LTD-SPONS ADR         Common Stock                 652487703       664,970      29,000    X               X
NOKIA ADR A                     Common Stock                 654902204     1,288,720      89,000    X               X
NORFOLK SOUTHERN CORP           Common Stock                 655844108     2,447,886     104,700    X               X
NUCOR CORP                      Common Stock                 670346105     1,430,880      22,000    X               X
NVIDIA CORP                     Common Stock                 67066G104       566,940      33,000    X               X
OMEGA WORLDWIDE INC             Common Stock                 68210B108        42,196      19,998    X               X
PEPSICO INC                     Common Stock                 713448108     1,205,000      25,000    X               X
PETROLEUM GEO-SVCS -SPON ADR    Common Stock                 716597109       342,000      95,000    X               X
PFIZER, INC.                    Common Stock                 717081103     5,757,500     164,500    X               X
PITNEY BOWES INC                Common Stock                 724479100     1,032,720      26,000    X               X
POWERWAVE TECHNOLOGIES INC      Common Stock                 739363109       833,560      91,000    X               X
PRICE LEGACY CORPORATION        Common Stock                 74144P106       171,972      44,668    X               X
QUANTA SERVICES INC             Common Stock                 74762E102       661,290      67,000    X               X
RADIANT SYSTEMS INC             Common Stock                 75025N102       495,140      38,000    X               X
RADIOSHACK CORP                 Common Stock                 750438103     1,052,100      35,000    X               X
ROYAL DUTCH PETROLEUM CO.       Common Stock                 780257804       331,620       6,000    X               X
SPX CORPORATION                 Common Stock                 784635104     2,115,000      18,000    X               X
SAKS INCORPORATED               Common Stock                 79377W108       616,320      48,000    X               X
SANDISK CORP                    Common Stock                 80004C101       285,200      23,000    X               X
SCHERING PLOUGH CORP            Common Stock                 806605101     3,119,477     126,808    X               X
SCHOLASTIC CORP                 Common Stock                 807066105     1,895,000      50,000    X               X
SHELL TRANSPORT - TRADING ADR   Common Stock                 822703609       900,200      20,000    X               X
SHIRE PHARMACEUTICALS           Common Stock                 82481R106       567,820      22,000    X               X
SIX FLAGS INC.                  Common Stock                 83001P109     1,011,500      70,000    X               X
STATE STREET CORP               Common Stock                 857477103     1,341,000      30,000    X               X
SUN MICROSYSTEMS, INC.          Common Stock                 866810104       646,290     129,000    X               X
SUNGARD DATA SYSTEMS            Common Stock                 867363103     2,118,400      80,000    X               X
SYMANTEC CORP                   Common Stock                 871503108     1,314,000      40,000    X               X
TARGET CORP                     Common Stock                 87612E106     1,981,200      52,000    X               X
TECHNITROL INC                  Common Stock                 878555101       932,000      40,000    X               X
TELLABS INC.                    Common Stock                 879664100       647,900     104,500    X               X
TENET HEALTHCARE CORP           Common Stock                 88033G100     3,219,750      45,000    X               X
TEXAS INSTRUMENTS               Common Stock                 882508104       734,700      31,000    X               X
TEXTRON, INC                    Common Stock                 883203101     2,016,700      43,000    X               X
TRIBUNE CO                      Common Stock                 896047107     4,089,000      94,000    X               X
TROPICAL SPORTSWEAR INTL        Common Stock                 89708P102       621,320      28,000    X               X
VF CORP.                        Common Stock                 918204108     1,372,350      35,000    X               X
VERIZON CORPORATION             Common Stock                 92343V104     1,405,250      35,000    X               X
VIACOM INC                      Common Stock                 925524100     1,333,800      30,000    X               X
VIACOM INC                      Common Stock                 925524308       525,341      11,840    X               X
WACHOVIA CORP. 2ND NEW COM      Common Stock                 929903102     2,863,500      75,000    X               X
WAL-MART STORES, INC.           Common Stock                 931142103       990,180      18,000    X               X
WALGREENS CO                    Common Stock                 931422109     4,539,025     117,500    X               X
WATSCO                          Common Stock                 942622101       223,200      12,000    X               X
WATSCO                          Common Stock                 942622200       565,750      31,000    X               X
WEYERHAEUSER CO                 Common Stock                 962166104     1,787,800      28,000    X               X
WINTRUST FINANCIAL CORP         Common Stock                 97650W108     1,833,939      53,050    X               X
WIRELESS TELECOM GROUP, INC.    Common Stock                 976524108       235,640     109,600    X               X
WORLDCOM INC                    Common Stock                 98157D106       110,888     133,600    X               X
WRIGLEY, (WM) JR. CO.           Common Stock                 982526105     1,273,050      23,000    X               X
WYETH                           Common Stock                 983024100       614,400      12,000    X               X
YAHOO ! INC.                    Common Stock                 984332106     1,114,712      75,523    X               X
YOUNG BROADCASTING CORP -A      Common Stock                 987434107     1,164,590      65,500    X               X
ZIMMER HOLDINGS INC             Common Stock                 98956P102       891,500      25,000    X               X
TRENWICK GROUP                  Common Stock                 G9032C109     4,351,493     580,199    X               X
AUDIOCODES LTD                  Common Stock                 M15342104       120,500      50,000    X               X
CKE RESTAURANTS INC             Taxable Bonds-Convertible    12561EAB1       977,288   1,095,000    X               X
CLEAR CHANNEL COMM              Taxable Bonds-Convertible    184502AE2       413,844     425,000    X               X
HILTON HOTELS CORP.             Taxable Bonds-Convertible    432848AL3       633,656     675,000    X               X
INTERIM SERVICES, INC.          Taxable Bonds-Convertible    45868PAA8       988,750   1,130,000    X               X
QUANTA SERVICES INC             Taxable Bonds-Convertible    74762EAA0     1,287,500   2,000,000    X               X