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

                                    Form 13F

                               Form 13F COVER PAGE

Report for the Calendar Year or Quarter Ended: September 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                November 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:    152

Form 13F Information Table Value Total:    $253,593
                                           (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

             COLUMN 1                COLUMN 2    COLUMN 3  COLUMN 4     COLUMN 5       COLUMN 6  COLUMN 7          COLUMN 8
--------------------------------- -------------- --------- -------- ----------------- ---------- -------- --------------------------
                                                            VALUE   SHRS OR  SH/ PUT/ INVESTMENT  OTHER         VOTING AUTHORITY
          NAME OF ISSUER          TITLE OF CLASS   CUSIP   (x$1000) PRN AMT  PRN CALL DISCRETION MANAGERS   SOLE    SHARED    NONE
--------------------------------- -------------- --------- -------- -------- --- ---- ---------- -------- -------- -------- --------
                                                                                           
ACM GOVT OPPOR FUND INC.          Common Stock   000918102   41,974  4612536 sh       Sole       None    4,612,536
AOL TIME WARNER                   Common Stock   00184A105    2,294   196081 sh       Sole       None      196,081
AT&T WIRELESS SERVICES            Common Stock   00209A106      252    61356 sh       Sole       None       61,356
ABBOTT LABORATORIES               Common Stock   002824100    1,212    30000 sh       Sole       None       30,000
ALCOA, INC.                       Common Stock   013817101    1,158    60000 sh       Sole       None       60,000
ALLIED WASTE INDUSTRIES INC       Common Stock   019589308      845   115018 sh       Sole       None      115,018
ALLTEL CORP.                      Common Stock   020039103    1,805    45000 sh       Sole       None       45,000
AMERICAN INTERNATIONAL GROUP      Common Stock   026874107    6,583   120361 sh       Sole       None      120,361
AMGEN, INC.                       Common Stock   031162100    2,326    55800 sh       Sole       None       55,800
ANADARKO PETROLEUM CORP           Common Stock   032511107    1,692    38000 sh       Sole       None       38,000
ANDREW CORPORATION                Common Stock   034425108      556    85000 sh       Sole       None       85,000
ANHEUSER-BUSCH COMPANIES INC      Common Stock   035229103    3,795    75000 sh       Sole       None       75,000
APACHE CORP.                      Common Stock   037411105    3,287    55300 sh       Sole       None       55,300
AVERY DENNISON CORP               Common Stock   053611109    1,424    25000 sh       Sole       None       25,000
BP AMOCO PLC                      Common Stock   055622104    2,992    75000 sh       Sole       None       75,000
BANKAMERICA CORP                  Common Stock   060505104    2,424    38000 sh       Sole       None       38,000
BIOGEN                            Common Stock   090597105      585    20000 sh       Sole       None       20,000
BRISTOL MYERS SQUIBB              Common Stock   110122108    1,380    58000 sh       Sole       None       58,000
BURLINGTON NORTHERN/SANTA FE      Common Stock   12189T104    1,124    47000 sh       Sole       None       47,000
CSX CORPORATION                   Common Stock   126408103    1,846    70000 sh       Sole       None       70,000
CVS CORPORATION                   Common Stock   126650100    1,014    40000 sh       Sole       None       40,000
CARDINAL HEALTH INC.              Common Stock   14149Y108    3,576    57500 sh       Sole       None       57,500
CARNIVAL CORP                     Common Stock   143658102    1,506    60000 sh       Sole       None       60,000
CHEVRON TEXACO CORP.              Common Stock   166764100    3,462    50000 sh       Sole       None       50,000
CISCO SYSTEMS                     Common Stock   17275R102      670    64000 sh       Sole       None       64,000
CITIGROUP, INC.                   Common Stock   172967101    3,175   107113 sh       Sole       None      107,113
CITRIX SYSTEMS INC                Common Stock   177376100      301    50000 sh       Sole       None       50,000
CLEAR CHANNEL COMM                Common Stock   184502102    2,932    84393 sh       Sole       None       84,393
COCA COLA CO                      Common Stock   191216100    2,613    54500 sh       Sole       None       54,500
COLGATE PALMOLIVE CO              Common Stock   194162103    2,589    48000 sh       Sole       None       48,000
COMVERSE TECHNOLOGY,INC           Common Stock   205862402      244    35000 sh       Sole       None       35,000
CONCORD EFS INC                   Common Stock   206197105      476    30000 sh       Sole       None       30,000
CORNING INC.                      Common Stock   219350105       88    55000 sh       Sole       None       55,000
DRS TECHNOLOGIES, INC.            Common Stock   23330X100      424    11400 sh       Sole       None       11,400
DEAN FOODS                        Common Stock   242370104    1,319    33168 sh       Sole       None       33,168
DEERE & CO                        Common Stock   244199105    2,181    48000 sh       Sole       None       48,000
DELL COMPUTER CORP                Common Stock   247025109    2,626   111700 sh       Sole       None      111,700
DELUXE CORP                       Common Stock   248019101    1,081    24000 sh       Sole       None       24,000
DEVON ENERGY                      Common Stock   25179M103    2,412    50000 sh       Sole       None       50,000
DIGITAL RIVER INC                 Common Stock   25388B104      230    30000 sh       Sole       None       30,000
THE WALT DISNEY CO.               Common Stock   254687106    1,514   100000 sh       Sole       None      100,000
DOW CHEMICAL                      Common Stock   260543103    1,447    53000 sh       Sole       None       53,000
EMC CORP./MASS                    Common Stock   268648102      251    55000 sh       Sole       None       55,000
EMERSON ELECTRIC CO.              Common Stock   291011104    2,109    48000 sh       Sole       None       48,000
ENGINEERED SUPPORT SYSTEMS INC    Common Stock   292866100      365     6400 sh       Sole       None        6,400
EQUITY OFFICE PROPERTIES TRUST    Common Stock   294741103    1,352    52373 sh       Sole       None       52,373
EXXON MOBIL CORP                  Common Stock   30231G102    5,321   166806 sh       Sole       None      166,806
FEDERAL HOME LOAN MTGE CORP       Common Stock   313400301      883    15800 sh       Sole       None       15,800
FEDERAL NATIONAL MORTGAGE ASSN    Common Stock   313586109    4,328    72700 sh       Sole       None       72,700
FIBERMARK INC                     Common Stock   315646109      274    32700 sh       Sole       None       32,700
FIRST DATA CORPORATION            Common Stock   319963104    1,695    60677 sh       Sole       None       60,677
FORD MOTOR COMPANY                Common Stock   345370860      856    87408 sh       Sole       None       87,408
FOUNDRY NETWORKS IN               Common Stock   35063R100       76    14000 sh       Sole       None       14,000
FOX ENTERTAINMENT GRP INC-A       Common Stock   35138T107      484    22000 sh       Sole       None       22,000
GENERAL ELECTRIC                  Common Stock   369604103    4,637   188136 sh       Sole       None      188,136
GENTEX CORP                       Common Stock   371901109      543    20000 sh       Sole       None       20,000
GENZYME CORP.                     Common Stock   372917104      585    28400 sh       Sole       None       28,400
GEORGIA-PACIFIC CORP              Common Stock   373298108      877    67000 sh       Sole       None       67,000
GETTY IMAGES, INC                 Common Stock   374276103    1,103    55000 sh       Sole       None       55,000
W.W. GRAINGER INC.                Common Stock   384802104    1,702    40000 sh       Sole       None       40,000
HCA INC                           Common Stock   404119109    1,904    40000 sh       Sole       None       40,000
HARTMARX                          Common Stock   417119104      198   101100 sh       Sole       None      101,100
HELMERICH AND PAYNE INC.          Common Stock   423452101      349    10200 sh       Sole       None       10,200
HEWLETT PACKARD CO.               Common Stock   428236103    1,073    91975 sh       Sole       None       91,975
HOME DEPOT INC                    Common Stock   437076102    2,272    87061 sh       Sole       None       87,061
HONEYWELL INTERNATIONAL INC.      Common Stock   438516106    1,050    48500 sh       Sole       None       48,500
HOUSEHOLD INTERNATIONAL INC       Common Stock   441815107    1,472    52000 sh       Sole       None       52,000
ILLINOIS TOOL WORKS INC.          Common Stock   452308109    2,333    40000 sh       Sole       None       40,000
INTEL CORPORATION                 Common Stock   458140100    1,194    86000 sh       Sole       None       86,000
INT'L BUSINESS MACHINES           Common Stock   459200101    3,148    54000 sh       Sole       None       54,000
INTERNATIONAL PAPER COMPANY       Common Stock   460146103      767    23000 sh       Sole       None       23,000
JOHNSON & JOHNSON                 Common Stock   478160104    6,518   120532 sh       Sole       None      120,532
KELLOGG CO.                       Common Stock   487836108    1,197    36000 sh       Sole       None       36,000
KROGER                            Common Stock   501044101    1,330    94368 sh       Sole       None       94,368
L-3 COMMUNICATIONS HLDGS INC      Common Stock   502424104    1,538    29200 sh       Sole       None       29,200
LIBERTY MEDIA CORP-A              Common Stock   530718105      430    60000 sh       Sole       None       60,000
ELI LILLY & CO.                   Common Stock   532457108    1,936    35000 sh       Sole       None       35,000
LITTELFUSE, INC.                  Common Stock   537008104      672    40000 sh       Sole       None       40,000
MGIC INVESTMENT CORP              Common Stock   552848103    1,020    25000 sh       Sole       None       25,000
MAY DEPT STORES                   Common Stock   577778103    1,434    63000 sh       Sole       None       63,000
MCDONALDS CORP                    Common Stock   580135101      423    24000 sh       Sole       None       24,000
MEDIMMUNE INC                     Common Stock   584699102      836    40000 sh       Sole       None       40,000
MERCK & CO.                       Common Stock   589331107    2,285    50000 sh       Sole       None       50,000
MERRILL LYNCH & CO.               Common Stock   590188108      988    30000 sh       Sole       None       30,000
MICROSOFT CORP.                   Common Stock   594918104    4,089    93500 sh       Sole       None       93,500
MOBILE MINI INC                   Common Stock   60740F105      739    57100 sh       Sole       None       57,100
MORGAN STANLEY DEAN WITTER & C    Common Stock   617446448    1,287    38000 sh       Sole       None       38,000
NANOPHASE TECHNOLOGIES            Common Stock   630079101      253    57800 sh       Sole       None       57,800
NASDAQ 100 SHARES                 Common Stock   631100104    1,257    60693 sh       Sole       None       60,693
NEWPARK RESOURCES INC.            Common Stock   651718504      493   124684 sh       Sole       None      124,684
NEWS CORP LTD-SPONS ADR           Common Stock   652487703      558    29000 sh       Sole       None       29,000
NOKIA ADR A                       Common Stock   654902204    1,179    89000 sh       Sole       None       89,000
NORFOLK SOUTHERN CORP             Common Stock   655844108    2,113   104700 sh       Sole       None      104,700
NORTHROP GRUMMAN CORP             Common Stock   666807102    1,488    12000 sh       Sole       None       12,000
NUCOR CORP                        Common Stock   670346105    1,516    40000 sh       Sole       None       40,000
NVIDIA CORP                       Common Stock   67066G104      282    33000 sh       Sole       None       33,000
PEPSICO INC                       Common Stock   713448108    1,533    41500 sh       Sole       None       41,500
PETROLEUM GEO-SVCS -SPON ADR      Common Stock   716597109       75    95000 sh       Sole       None       95,000
PFIZER, INC.                      Common Stock   717081103    4,773   164500 sh       Sole       None      164,500
PITNEY BOWES INC                  Common Stock   724479100      792    26000 sh       Sole       None       26,000
BANCO POPULAR                     Common Stock   733174106       83     2640 sh       Sole       None        2,641
POWERWAVE TECHNOLOGIES INC        Common Stock   739363109      308    91000 sh       Sole       None       91,000
PRICE LEGACY CORPORATION          Common Stock   74144P106      130    44668 sh       Sole       None       44,668
PROCTOR & GAMBLE CO               Common Stock   742718109      849     9500 sh       Sole       None        9,500
QUANTA SERVICES INC               Common Stock   74762E102      139    67000 sh       Sole       None       67,000
RADIANT SYSTEMS INC               Common Stock   75025N102      304    38000 sh       Sole       None       38,000
RADIOSHACK CORP                   Common Stock   750438103      702    35000 sh       Sole       None       35,000
ROYAL DUTCH PETROLEUM CO.         Common Stock   780257804      241     6000 sh       Sole       None        6,000
SPDR S&P DEP RCPT TRADES/QUOTE    Common Stock   78462F103      627     7669 sh       Sole       None        7,669
SPX CORPORATION                   Common Stock   784635104    2,522    25000 sh       Sole       None       25,000
SAFEWAY INC.                      Common Stock   786514208    1,115    50000 sh       Sole       None       50,000
SAKS INCORPORATED                 Common Stock   79377W108      505    48000 sh       Sole       None       48,000
SANDISK CORP                      Common Stock   80004C101      301    23000 sh       Sole       None       23,000
SCHERING PLOUGH CORP              Common Stock   806605101    2,703   126808 sh       Sole       None      126,808
SCHOLASTIC CORP                   Common Stock   807066105    2,234    50000 sh       Sole       None       50,000
SHELL TRANSPORT - TRADING ADR     Common Stock   822703609      714    20000 sh       Sole       None       20,000
SHIRE PHARMACEUTICALS             Common Stock   82481R106      743    30000 sh       Sole       None       30,000
SIGMA ALDRICH                     Common Stock   826552101    1,872    38000 sh       Sole       None       38,000
SIX FLAGS INC.                    Common Stock   83001P109      246    70000 sh       Sole       None       70,000
STATE STREET CORP                 Common Stock   857477103    1,159    30000 sh       Sole       None       30,000
SUN MICROSYSTEMS, INC.            Common Stock   866810104      334   129000 sh       Sole       None      129,000
SUNGARD DATA SYSTEMS              Common Stock   867363103    1,556    80000 sh       Sole       None       80,000
SYMANTEC CORP                     Common Stock   871503108    1,345    40000 sh       Sole       None       40,000
TARGET CORP                       Common Stock   87612E106    1,535    52000 sh       Sole       None       52,000
TECHNITROL INC                    Common Stock   878555101      598    40000 sh       Sole       None       40,000
TELLABS INC.                      Common Stock   879664100      425   104500 sh       Sole       None      104,500
TENET HEALTHCARE CORP             Common Stock   88033G100    2,227    45000 sh       Sole       None       45,000
TEXAS INSTRUMENTS                 Common Stock   882508104      635    43000 sh       Sole       None       43,000
TEXTRON, INC                      Common Stock   883203101    1,466    43000 sh       Sole       None       43,000
TRIBUNE CO                        Common Stock   896047107    3,930    94000 sh       Sole       None       94,000
TROPICAL SPORTSWEAR INTL          Common Stock   89708P102      363    28000 sh       Sole       None       28,000
VF CORP.                          Common Stock   918204108    1,259    35000 sh       Sole       None       35,000
VERIZON CORPORATION               Common Stock   92343V104      960    35000 sh       Sole       None       35,000
VIACOM INC                        Common Stock   925524100    1,216    30000 sh       Sole       None       30,000
WAL-MART STORES, INC.             Common Stock   931142103    1,920    39000 sh       Sole       None       39,000
WALGREENS CO                      Common Stock   931422109    3,614   117500 sh       Sole       None      117,500
WATSCO                            Common Stock   942622101      168    12000 sh       Sole       None       12,000
WATSCO                            Common Stock   942622200      443    31000 sh       Sole       None       31,000
WENDY'S INTERNATIONAL             Common Stock   950590109    1,291    39000 sh       Sole       None       39,000
WEYERHAEUSER CO                   Common Stock   962166104    1,531    35000 sh       Sole       None       35,000
WINTRUST FINANCIAL CORP           Common Stock   97650W108    1,519    53050 sh       Sole       None       53,050
WIRELESS TELECOM GROUP, INC.      Common Stock   976524108      215   109600 sh       Sole       None      109,600
WORLDCOM INC                      Common Stock   98157D106        9    92000 sh       Sole       None       92,000
WRIGLEY, (WM) JR. CO.             Common Stock   982526105    1,484    30000 sh       Sole       None       30,000
WYETH                             Common Stock   983024100      381    12000 sh       Sole       None       12,000
YAHOO ! INC.                      Common Stock   984332106      722    75522 sh       Sole       None       75,523
YOUNG BROADCASTING CORP -A        Common Stock   987434107      567    65500 sh       Sole       None       65,500
ZIMMER HOLDINGS INC               Common Stock   98956P102      958    25000 sh       Sole       None       25,000
AUDIOCODES LTD                    Common Stock   M15342104       90    50000 sh       Sole       None       50,000
KERZNER INTERNATIONAL LTD         Common Stock   P6065Y107      276    12000 sh       Sole       None       12,000
CLEAR CHANNEL COMM                Taxble Bnds-Con184502AE2      420   425000 prn      Sole       None            0
QUANTA SERVICES INC               Taxble Bnds-Con74762EAA0      970  2000000 prn      Sole       None            0