As filed with the Securities and Exchange Commission on June 1, 1998.

                                                  Registration No. 333-________

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                     ---------------------------------------

                                    FORM S-8

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                     --------------------------------------

                                 AON CORPORATION
               (Exact name of issuer as specified in its charter)



          Delaware                                       36-3051915
(State or other jurisdiction of                       (I.R.S. Employer
incorporation or organization)                        Identification No.)



                     --------------------------------------

           AON STOCK AWARD PLAN (as amended and restated through 1997)
          AON STOCK OPTION PLAN (as amended and restated through 1997)
                      AON 1998 EMPLOYEE STOCK PURCHASE PLAN
                 RATH & STRONG, INC. EMPLOYEES' STOCK BONUS PLAN

                            (Full title of the plans)
                      -------------------------------------


     Raymond I. Skilling, Esq.
   Executive Vice President and
          Chief Counsel                                     Copy to:
      123 North Wacker Drive                   Jerome S. Hanner, Senior Counsel
     Chicago, Illinois   60606                           Aon Corporation
     (Name and address of agent                       123 North Wacker Drive
          for service)                               Chicago, Illinois   60606
          (312) 701-3025
   (Telephone Number, including
  area code, of agent for service)


<PAGE>
<TABLE>
<CAPTION>
                         CALCULATION OF REGISTRATION FEE

|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|Title of                |Amount to Be          |Proposed Maximum      |Proposed Maximum      |Amount of             |
|Securities to be        |Registered(1)         |Offering Price Per    |Aggregate Offering    |Registration Fee(2)   |
|Registered              |                      |Share(2)              |Price(2)              |                      |
|                        |                      |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
<S>                            <C>                      <C>            <C>                          <C>
|Common Stock            |      3,575,500       |        $64.06        |$229,014,500.00       |      $67,560.00      |
|$1.00 par value per     |Aon Stock Award Plan  |                      |                      |                      |
|share                   |(as amended and       |                      |                      |                      |
|                        |restated through      |                      |                      |                      |
|                        |1997)                 |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|Common Stock            |      4,000,000       |        $64.06        |$256,240,000.00       |      $75,591.00      |
|$1.00 par value per     |Aon Stock Option      |                      |                      |                      |
|share                   |Plan (as amended and  |                      |                      |                      |
|                        |restated through      |                      |                      |                      |
|                        |1997)                 |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|Common Stock            |     5,000,000        |        $64.06        |$320,300,000.00       |     $94,489.00       |
|$1.00 par value per     |Aon 1998 Employee     |                      |                      |                      |
|share                   |Stock Purchase Plan   |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|Common Stock            |         57,654       |        $64.06        |  $3,693,316.00       |      $1,090.00       |
|$1.00 par value per     |Rath & Strong         |                      |                      |                      |
|share                   |Employees' Stock      |                      |                      |                      |
|                        |Bonus Plan            |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|                        |                      |                      |                      |Total Fees:           |
|                        |                      |                      |                      |    $238,730.00       |
|------------------------|----------------------|----------------------|----------------------|----------------------|
<FN>
(1)      Pursuant to Rule 416 under the  Securities  Act of 1933,  includes such
         indeterminant  number  of shares  as may be  issuable  by reason of the
         operation of the anti-dilution provisions of the plans listed below.

(2)      Estimated solely for the purpose of calculating  the  registration  fee
         and,  pursuant to Rule 457(h) under the Securities  Act of 1933,  based
         upon the average of the high and low sale prices of the Common Stock of
         the Registrant on the New York Stock Exchange on May 27, 1998.
</FN>
</TABLE>


<PAGE>
                                     PART I
              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS


         The document(s)  containing the information specified in Part I of Form
S-8  have  been or will be sent or  given  to  employees  as  specified  by Rule
428(b)(1) under the Securities Act of 1933, as amended.


                                     PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.   INCORPORATION OF DOCUMENTS BY REFERENCE

         The  following   documents  are   incorporated   by  reference  in  the
registration statement:

         (c)      The  Registrant's  Annual  Report on Form 10-K for the  fiscal
                  year ended  December 31, 1997 filed  pursuant to Section 13(a)
                  of the Securities Exchange Act of 1934.

         (d)      The Registrant's Quarterly Report on Form 10-Q for the quarter
                  ended  March 31, 1998 filed  pursuant to Section  13(a) of the
                  Securities Exchange Act of 1934.

         (e)      All other reports filed by the Registrant pursuant to Sections
                  13(a) or 15(d) of the  Securities  Exchange  Act of 1934 since
                  December 31, 1997.

         (f)      The  description of Aon  Corporation  common stock,  $1.00 par
                  value  per  share  (the  "Common  Stock")   contained  in  the
                  Registrant's  registration  statement  on Form 8-A filed under
                  the  Securities  Exchange  Act  of  1934  (File  No.  1-7933),
                  including  any  amendment  or report  filed for the purpose of
                  updating such description.

         All documents  subsequently filed by the Registrant pursuant to Section
13(a),  13(c), 14 and 15(d) of the Securities Exchange Act of 1934, prior to the
filing of a  post-effective  amendment  which  indicates that all shares offered
have been sold or which deregisters all shares then remaining  unsold,  shall be
deemed to be incorporated by reference in the  registration  statement and to be
part hereof from the date of filing of such documents.

Item 5.  INTEREST OF NAMED EXPERTS AND COUNSEL

         The validity of the issuance of the Common  Stock  offered  pursuant to
the plans registered  hereunder will be passed upon for the Registrant by Jerome
S. Hanner,  Senior  Counsel of the  Registrant.  As of May 27, 1998,  Mr. Hanner
owned 4,681 shares of Common Stock.

                                      II-1
<PAGE>

Item 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         The  Registrant's   Certificate  of  Incorporation  provides  that  the
Registrant  shall  indemnify  each director and officer of the Registrant to the
fullest extent  permitted by law,  subject to the  limitations  set forth in its
By-Laws.  The By-Laws provide that the Registrant shall indemnify to the fullest
extent  permitted by law any person made or threatened to be made a party to any
action,  suit  or  proceeding,   whether  civil,  criminal,   administrative  or
investigative,  by reason of the fact that such  person is or was a director  or
officer of the  Registrant or serves or served at the request of the  Registrant
any other enterprise as a director or officer.

         Section  145 of the  General  Corporation  Law of the State of Delaware
provides  for the  indemnification  of  directors  and  officers  under  certain
circumstances, as therein set forth.


Item 8.  EXHIBITS

         The following are filed as exhibits to this registration statement:

  4.1    Second  Restated  Certificate  of  Incorporation  of the  Registrant --
         incorporated  by reference to Exhibit 3(a) to the  Registrant's  Annual
         Report on Form 10-K for the year ended December 31, 1991.

  4.2    Certificate   of  Amendment  of  the   Registrant's   Second   Restated
         Certificate of Incorporation -incorporated by reference to Exhibit 3 to
         the  Registrant's  Quarterly Report on Form 10-Q for the quarter ending
         March 31, 1994.

  4.3    Bylaws of the Registrant --  incorporated  by referenced to Exhibit (d)
         to the  Registrant's  Annual  Report  on Form  10-K for the year  ended
         December 31, 1982.

  4.4    Aon Stock  Award  Plan (as  amended  through  1997) -  incorporated  by
         reference to Exhibit 10(b) to the Registrant's Quarterly Report on Form
         10-Q for the quarter ended March 31, 1997.

  4.5    Aon Stock  Option Plan (as amended  through  1997) --  incorporated  by
         reference to Exhibit 10(a) to the Registrant's Quarterly Report on Form
         10-Q for the quarter ended March 31, 1997.

  4.6    Aon 1998 Employee Stock Purchase Plan --  incorporated  by reference to
         Exhibit 10 to the  Registrant's  Quarterly  Report on Form 10-Q for the
         quarter ended March 31, 1998.

  4.7    Rath & Strong, Inc. Employees' Stock Bonus Plan.


                                      II-2
<PAGE>
   5.    Opinion of Jerome S. Hanner, Senior Counsel of the Registrant.

  15.    Acknowledgment of Ernst & Young LLP.

  23.1   Consent of Ernst & Young LLP.

  23.2   Consent of Jerome S. Hanner  (contained in the opinion filed as Exhibit
         5 to the registration statement).


Item 9.  UNDERTAKINGS

         The Registrant hereby undertakes:

         (1) To file, during any period in which offers or sales are being made,
a post-effective amendment to this Registration Statement:

                  (i)      to  include  any   prospectus   required  by  Section
                           10(a)(3) of the Securities Act of 1933;

                  (ii)     to  reflect  in the  prospectus  any  facts or events
                           arising after the effective date of the  registration
                           statement   (or  the   most   recent   post-effective
                           amendment  thereof)  which,  individually  or in  the
                           aggregate,  represent  a  fundamental  change  in the
                           information set forth in the registration  statement;
                           and

                  (iii)    to include any material  information  with respect to
                           the plan of distribution not previously  disclosed in
                           the registration  statement or any material change to
                           such information in the registration statement;

         provided,  however,  that paragraphs (1)(i) and (1)(ii) do not apply if
the information  required to be included in a post-effective  amendment by those
paragraphs is contained in periodic reports filed by the registrant  pursuant to
Section  13 or Section  15(d) of the  Securities  Exchange  Act of 1934 that are
incorporated by reference in the registration statement.

         (2) That,  for the  purpose  of  determining  any  liability  under the
Securities Act of 1933 (the "Act"), each such post-effective  amendment shall be
deemed to be a new  registration  statement  relating to the securities  offered
therein,  and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

         (3) To remove from registration by means of a post-effective  amendment
any of the securities being registered which remain unsold at the termination of
the offering.


                                      II-3
<PAGE>
         (4) That, for the purposes of determining  any liability under the Act,
each filing of the  Registrant's  annual  report  pursuant  to Section  13(a) or
Section 15(d) of the  Securities  Exchange Act of 1934 that is  incorporated  by
reference in the registration statement shall be deemed to be a new registration
statement relating to the securities  offered therein,  and the offering of such
securities  at that time shall be deemed to be the  initial  bona fide  offering
thereof.

         (5) Insofar as  indemnification  for liabilities  arising under the Act
may  be  permitted  to  directors,  officers  and  controlling  persons  of  the
Registrant  pursuant to the  provisions  described in Item 6 or  otherwise,  the
Registrant  has been advised that in the opinion of the  Securities and Exchange
Commission such indemnification is against public policy as expressed in the Act
and is, therefore,  unenforceable. In the event that a claim for indemnification
against such  liabilities  (other than the payment by the Registrant of expenses
incurred or paid by a director,  officer or controlling person of the Registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director,  officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been  settled by  controlling  precedent,  submit to a court of  appropriate
jurisdiction the question whether such  indemnification  by it is against public
policy as expressed in the Act and will be governed by the final adjudication of
such issue.


                                      II-4
<PAGE>

                                   SIGNATURES

         Pursuant  to the  requirements  of the  Securities  Act  of  1933,  the
Registrant certifies that it has reasonable grounds to believe that it meets all
the  requirements  for filing on Form S-8 and has duly caused this  registration
statement  to be  signed  on its  behalf  by  the  undersigned,  thereunto  duly
authorized, in the City of Chicago, State of Illinois, on May 27, 1998.

                                               Aon Corporation



                                               By:   /S/ PATRICK G. RYAN
                                                  -----------------------------
                                                     Patrick G. Ryan, Chairman,
                                                     President and Chief
                                                     Executive Officer


         Each person whose  signature  appears  below  constitutes  and appoints
Patrick G. Ryan, Raymond I. Skilling,  and Jerome S. Hanner, and each of them as
his true and lawful  attorney-in-fact and agent, with full power of substitution
and  resubstitution,  for him and in his name,  pace and  stead,  in any and all
capacities,  to sign any and all amendments to this registration statement,  and
to file the same with all exhibits  thereto,  and other  documents in connection
therewith,  with the  Securities  and Exchange  Commission,  granting  unto said
attorney-in-fact  and agent full power and  authority to do and perform each act
and thing  requisite  and  necessary  to be done,  as fully to all  intents  and
purposes as he might or could do in person,  hereby ratifying and confirming all
that said  attorney-in-fact  and agent,  or his substitute or  substitutes,  may
lawfully do or cause to be done by virtue hereof.

         Pursuant  to the  requirements  of the  Securities  Act of  1933,  this
registration  statement and the  foregoing  power of attorney has been signed by
the following persons in the capacities and on the dates indicated.



SIGNATURE                          TITLE                           DATE


/S/ PATRICK G. RYAN                Chairman,                        May 27, 1998
----------------------
(Patrick G. Ryan)                  President,  Chief Executive
                                   Officer and Director
                                   (Principal Executive Officer)


                                      II-5
<PAGE>

/S/ DANIEL T. CARROLL
----------------------
(Daniel T. Carroll)                Director                         May 27, 1998



----------------------
(Franklin A. Cole)                 Director                       ________, 1998



/S/ EDGAR D. JANNOTTA
----------------------
(Edgar D. Jannotta)                Director                         May 27, 1998

/S/ PERRY J. LEWIS
----------------------
(Perry J. Lewis)                   Director                         May 27, 1998


/S/ ANDREW J. MCKENNA
----------------------
(Andrew J. McKenna)                Director                         May 27, 1998


/S/ NEWTON N. MINOW
----------------------
(Newton N. Minow)                  Director                         May 27, 1998


/S/ RICHARD C. NOTEBAERT
----------------------
(Richard C. Notebaert)             Director                         May 27, 1998


/S/ DONALD S. PERKINS
----------------------
(Donald S. Perkins)                Director                         May 27, 1998


/S/ JOHN W. ROGERS, JR.
----------------------
(John W. Rogers, Jr.)              Director                         May 27, 1998


/S/ GEORGE A. SCHAEFER
----------------------
(George A. Schaefer)               Director                         May 27, 1998


                                      II-6
<PAGE>

/S/ RAYMOND I. SKILLING
----------------------
(Raymond I. Skilling)              Director                         May 27, 1998


/S/ FRED L. TURNER
----------------------
(Fred L. Turner)                   Director                         May 27, 1998


/S/ ARNOLD R. WEBER
----------------------
(Arnold R. Weber)                  Director                         May 27, 1998


----------------------
(Carolyn Y. Woo)                   Director                       ________, 1998


/S/ HARVEY N. MEDVIN
----------------------
(Harvey N. Medvin)                 Executive Vice President and     May 27, 1998
                                   Chief Financial Officer (Principal
                                   Financial and Accounting Officer)


                                      II-7
<PAGE>
                                  EXHIBIT INDEX


EXHIBIT NO.        DESCRIPTION

4.1            Second Restated  Certificate of  Incorporation  of
               the  Registrant  --incorporated  by  reference  to
               Exhibit 3(a) to the Registrant's  Annual Report on
               Form 10-K for the year ended December 31, 1991.


4.2            Certificate  of  Amendment  of  the   Registrant's
               Second Restated  Certificate of  Incorporation  --
               incorporated  by  reference  to  Exhibit  4 to the
               Registrant's Quarterly Report on Form 10-Q for the
               quarter ending March 31, 1994.


4.3            Bylaws  of  the  Registrant  --   incorporated  by
               referenced  to  Exhibit  (d) to  the  Registrant's
               Annual  Report  on Form  10-K for the  year  ended
               December 31, 1982.

4.4            Aon Stock  Award  Plan (as  amended  and  restated
               through  1997) --  incorporated  by  reference  to
               Exhibit 10(b) to the Registrant's Quarterly Report
               on Form 10-Q for the quarter ended March 31, 1997.


4.5            Aon Stock  Option Plan (as  amended  and  restated
               through 1997) incorporated by reference to Exhibit
               10(a) to the Registrant's Quarterly Report on Form
               10-Q for the quarter ended March 31, 1997.


4.6            Aon   1998   Employee   Stock   Purchase   Plan  -
               incorporated  by  reference  to  Exhibit 10 to the
               Registrant's Quarterly Report on Form 10-Q for the
               quarter ended March 31, 1998.


4.7            Rath & Strong, Inc. Employees' Stock Bonus Plan.

5              Opinion of Jerome S. Hanner, Senior Counsel of the
               Registrant.


15             Acknowledgment of Ernst & Young LLP.

23.1           Consent of Ernst & Young LLP.

23.2           Consent  of Jerome  S.  Hanner  (contained  in the
               opinion  filed as  Exhibit  5 to the  registration
               statement).


                              II-8
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 23409}]
{"company-data": {"conformed-name": "AON CORP", "cik": "0000315293", "assigned-sic": "6321", "irs-number": "363051915", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-55773", "film-number": "98640808"}, "business-address": {"street1": "123 N WACKER DR", "city": "CHICAGO", "state": "IL", "zip": "60606", "phone": "3127013000"}, "former-company": {"former-conformed-name": "COMBINED INTERNATIONAL CORP", "date-changed": "19870504"}}
As filed with the Securities and Exchange Commission on June 1, 1998.

                                                  Registration No. 333-________

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                     ---------------------------------------

                                    FORM S-8

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                     --------------------------------------

                                 AON CORPORATION
               (Exact name of issuer as specified in its charter)

          Delaware                                       36-3051915
(State or other jurisdiction of                       (I.R.S. Employer
incorporation or organization)                        Identification No.)

                     --------------------------------------

           AON STOCK AWARD PLAN (as amended and restated through 1997)
          AON STOCK OPTION PLAN (as amended and restated through 1997)
                      AON 1998 EMPLOYEE STOCK PURCHASE PLAN
                 RATH & STRONG, INC. EMPLOYEES' STOCK BONUS PLAN

                            (Full title of the plans)
                      -------------------------------------

     Raymond I. Skilling, Esq.
   Executive Vice President and
          Chief Counsel                                     Copy to:
      123 North Wacker Drive                   Jerome S. Hanner, Senior Counsel
     Chicago, Illinois   60606                           Aon Corporation
     (Name and address of agent                       123 North Wacker Drive
          for service)                               Chicago, Illinois   60606
          (312) 701-3025
   (Telephone Number, including
  area code, of agent for service)
CALCULATION OF REGISTRATION FEE

|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|Title of                |Amount to Be          |Proposed Maximum      |Proposed Maximum      |Amount of             |
|Securities to be        |Registered(1)         |Offering Price Per    |Aggregate Offering    |Registration Fee(2)   |
|Registered              |                      |Share(2)              |Price(2)              |                      |
|                        |                      |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|Common Stock            |      3,575,500       |        $64.06        |$229,014,500.00       |      $67,560.00      |
|$1.00 par value per     |Aon Stock Award Plan  |                      |                      |                      |
|share                   |(as amended and       |                      |                      |                      |
|                        |restated through      |                      |                      |                      |
|                        |1997)                 |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|Common Stock            |      4,000,000       |        $64.06        |$256,240,000.00       |      $75,591.00      |
|$1.00 par value per     |Aon Stock Option      |                      |                      |                      |
|share                   |Plan (as amended and  |                      |                      |                      |
|                        |restated through      |                      |                      |                      |
|                        |1997)                 |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|Common Stock            |     5,000,000        |        $64.06        |$320,300,000.00       |     $94,489.00       |
|$1.00 par value per     |Aon 1998 Employee     |                      |                      |                      |
|share                   |Stock Purchase Plan   |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|Common Stock            |         57,654       |        $64.06        |  $3,693,316.00       |      $1,090.00       |
|$1.00 par value per     |Rath & Strong         |                      |                      |                      |
|share                   |Employees' Stock      |                      |                      |                      |
|                        |Bonus Plan            |                      |                      |                      |
|------------------------|----------------------|----------------------|----------------------|----------------------|
|------------------------|----------------------|----------------------|----------------------|----------------------|
|                        |                      |                      |                      |                      |
|                        |                      |                      |                      |Total Fees:           |
|                        |                      |                      |                      |    $238,730.00       |
|------------------------|----------------------|----------------------|----------------------|----------------------|
(1)      Pursuant to Rule 416 under the  Securities  Act of 1933,  includes such
         indeterminant  number  of shares  as may be  issuable  by reason of the
         operation of the anti-dilution provisions of the plans listed below.

(2)      Estimated solely for the purpose of calculating  the  registration  fee
         and,  pursuant to Rule 457(h) under the Securities  Act of 1933,  based
         upon the average of the high and low sale prices of the Common Stock of
         the Registrant on the New York Stock Exchange on May 27, 1998.
PART I
              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

         The document(s)  containing the information specified in Part I of Form
S-8  have  been or will be sent or  given  to  employees  as  specified  by Rule
428(b)(1) under the Securities Act of 1933, as amended.

                                     PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.   INCORPORATION OF DOCUMENTS BY REFERENCE

         The  following   documents  are   incorporated   by  reference  in  the
registration statement:

         (c)      The  Registrant's  Annual  Report on Form 10-K for the  fiscal
                  year ended  December 31, 1997 filed  pursuant to Section 13(a)
                  of the Securities Exchange Act of 1934.

         (d)      The Registrant's Quarterly Report on Form 10-Q for the quarter
                  ended  March 31, 1998 filed  pursuant to Section  13(a) of the
                  Securities Exchange Act of 1934.

         (e)      All other reports filed by the Registrant pursuant to Sections
                  13(a) or 15(d) of the  Securities  Exchange  Act of 1934 since
                  December 31, 1997.

         (f)      The  description of Aon  Corporation  common stock,  $1.00 par
                  value  per  share  (the  "Common  Stock")   contained  in  the
                  Registrant's  registration  statement  on Form 8-A filed under
                  the  Securities  Exchange  Act  of  1934  (File  No.  1-7933),
                  including  any  amendment  or report  filed for the purpose of
                  updating such description.

         All documents  subsequently filed by the Registrant pursuant to Section
13(a),  13(c), 14 and 15(d) of the Securities Exchange Act of 1934, prior to the
filing of a  post-effective  amendment  which  indicates that all shares offered
have been sold or which deregisters all shares then remaining  unsold,  shall be
deemed to be incorporated by reference in the  registration  statement and to be
part hereof from the date of filing of such documents.

Item 5.  INTEREST OF NAMED EXPERTS AND COUNSEL

         The validity of the issuance of the Common  Stock  offered  pursuant to
the plans registered  hereunder will be passed upon for the Registrant by Jerome
S. Hanner,  Senior  Counsel of the  Registrant.  As of May 27, 1998,  Mr. Hanner
owned 4,681 shares of Common Stock.

                                      II-1
Item 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         The  Registrant's   Certificate  of  Incorporation  provides  that  the
Registrant  shall  indemnify  each director and officer of the Registrant to the
fullest extent  permitted by law,  subject to the  limitations  set forth in its
By-Laws.  The By-Laws provide that the Registrant shall indemnify to the fullest
extent  permitted by law any person made or threatened to be made a party to any
action,  suit  or  proceeding,   whether  civil,  criminal,   administrative  or
investigative,  by reason of the fact that such  person is or was a director  or
officer of the  Registrant or serves or served at the request of the  Registrant
any other enterprise as a director or officer.

         Section  145 of the  General  Corporation  Law of the State of Delaware
provides  for the  indemnification  of  directors  and  officers  under  certain
circumstances, as therein set forth.

Item 8.  EXHIBITS

         The following are filed as exhibits to this registration statement:

  4.1    Second  Restated  Certificate  of  Incorporation  of the  Registrant --
         incorporated  by reference to Exhibit 3(a) to the  Registrant's  Annual
         Report on Form 10-K for the year ended December 31, 1991.

  4.2    Certificate   of  Amendment  of  the   Registrant's   Second   Restated
         Certificate of Incorporation -incorporated by reference to Exhibit 3 to
         the  Registrant's  Quarterly Report on Form 10-Q for the quarter ending
         March 31, 1994.

  4.3    Bylaws of the Registrant --  incorporated  by referenced to Exhibit (d)
         to the  Registrant's  Annual  Report  on Form  10-K for the year  ended
         December 31, 1982.

  4.4    Aon Stock  Award  Plan (as  amended  through  1997) -  incorporated  by
         reference to Exhibit 10(b) to the Registrant's Quarterly Report on Form
         10-Q for the quarter ended March 31, 1997.

  4.5    Aon Stock  Option Plan (as amended  through  1997) --  incorporated  by
         reference to Exhibit 10(a) to the Registrant's Quarterly Report on Form
         10-Q for the quarter ended March 31, 1997.

  4.6    Aon 1998 Employee Stock Purchase Plan --  incorporated  by reference to
         Exhibit 10 to the  Registrant's  Quarterly  Report on Form 10-Q for the
         quarter ended March 31, 1998.

  4.7    Rath & Strong, Inc. Employees' Stock Bonus Plan.

                                      II-2
5.    Opinion of Jerome S. Hanner, Senior Counsel of the Registrant.

  15.    Acknowledgment of Ernst & Young LLP.

  23.1   Consent of Ernst & Young LLP.

  23.2   Consent of Jerome S. Hanner  (contained in the opinion filed as Exhibit
         5 to the registration statement).

Item 9.  UNDERTAKINGS

         The Registrant hereby undertakes:

         (1) To file, during any period in which offers or sales are being made,
a post-effective amendment to this Registration Statement:

                  (i)      to  include  any   prospectus   required  by  Section
                           10(a)(3) of the Securities Act of 1933;

                  (ii)     to  reflect  in the  prospectus  any  facts or events
                           arising after the effective date of the  registration
                           statement   (or  the   most   recent   post-effective
                           amendment  thereof)  which,  individually  or in  the
                           aggregate,  represent  a  fundamental  change  in the
                           information set forth in the registration  statement;
                           and

                  (iii)    to include any material  information  with respect to
                           the plan of distribution not previously  disclosed in
                           the registration  statement or any material change to
                           such information in the registration statement;

         provided,  however,  that paragraphs (1)(i) and (1)(ii) do not apply if
the information  required to be included in a post-effective  amendment by those
paragraphs is contained in periodic reports filed by the registrant  pursuant to
Section  13 or Section  15(d) of the  Securities  Exchange  Act of 1934 that are
incorporated by reference in the registration statement.

         (2) That,  for the  purpose  of  determining  any  liability  under the
Securities Act of 1933 (the "Act"), each such post-effective  amendment shall be
deemed to be a new  registration  statement  relating to the securities  offered
therein,  and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

         (3) To remove from registration by means of a post-effective  amendment
any of the securities being registered which remain unsold at the termination of
the offering.

                                      II-3
(4) That, for the purposes of determining  any liability under the Act,
each filing of the  Registrant's  annual  report  pursuant  to Section  13(a) or
Section 15(d) of the  Securities  Exchange Act of 1934 that is  incorporated  by
reference in the registration statement shall be deemed to be a new registration
statement relating to the securities  offered therein,  and the offering of such
securities  at that time shall be deemed to be the  initial  bona fide  offering
thereof.

         (5) Insofar as  indemnification  for liabilities  arising under the Act
may  be  permitted  to  directors,  officers  and  controlling  persons  of  the
Registrant  pursuant to the  provisions  described in Item 6 or  otherwise,  the
Registrant  has been advised that in the opinion of the  Securities and Exchange
Commission such indemnification is against public policy as expressed in the Act
and is, therefore,  unenforceable. In the event that a claim for indemnification
against such  liabilities  (other than the payment by the Registrant of expenses
incurred or paid by a director,  officer or controlling person of the Registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director,  officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been  settled by  controlling  precedent,  submit to a court of  appropriate
jurisdiction the question whether such  indemnification  by it is against public
policy as expressed in the Act and will be governed by the final adjudication of
such issue.

                                      II-4
SIGNATURES

         Pursuant  to the  requirements  of the  Securities  Act  of  1933,  the
Registrant certifies that it has reasonable grounds to believe that it meets all
the  requirements  for filing on Form S-8 and has duly caused this  registration
statement  to be  signed  on its  behalf  by  the  undersigned,  thereunto  duly
authorized, in the City of Chicago, State of Illinois, on May 27, 1998.

                                               Aon Corporation

                                               By:   /S/ PATRICK G. RYAN
                                                  -----------------------------
                                                     Patrick G. Ryan, Chairman,
                                                     President and Chief
                                                     Executive Officer

         Each person whose  signature  appears  below  constitutes  and appoints
Patrick G. Ryan, Raymond I. Skilling,  and Jerome S. Hanner, and each of them as
his true and lawful  attorney-in-fact and agent, with full power of substitution
and  resubstitution,  for him and in his name,  pace and  stead,  in any and all
capacities,  to sign any and all amendments to this registration statement,  and
to file the same with all exhibits  thereto,  and other  documents in connection
therewith,  with the  Securities  and Exchange  Commission,  granting  unto said
attorney-in-fact  and agent full power and  authority to do and perform each act
and thing  requisite  and  necessary  to be done,  as fully to all  intents  and
purposes as he might or could do in person,  hereby ratifying and confirming all
that said  attorney-in-fact  and agent,  or his substitute or  substitutes,  may
lawfully do or cause to be done by virtue hereof.

         Pursuant  to the  requirements  of the  Securities  Act of  1933,  this
registration  statement and the  foregoing  power of attorney has been signed by
the following persons in the capacities and on the dates indicated.

SIGNATURE                          TITLE                           DATE

/S/ PATRICK G. RYAN                Chairman,                        May 27, 1998
----------------------
(Patrick G. Ryan)                  President,  Chief Executive
                                   Officer and Director
                                   (Principal Executive Officer)

                                      II-5
/S/ DANIEL T. CARROLL
----------------------
(Daniel T. Carroll)                Director                         May 27, 1998

----------------------
(Franklin A. Cole)                 Director                       ________, 1998

/S/ EDGAR D. JANNOTTA
----------------------
(Edgar D. Jannotta)                Director                         May 27, 1998

/S/ PERRY J. LEWIS
----------------------
(Perry J. Lewis)                   Director                         May 27, 1998

/S/ ANDREW J. MCKENNA
----------------------
(Andrew J. McKenna)                Director                         May 27, 1998

/S/ NEWTON N. MINOW
----------------------
(Newton N. Minow)                  Director                         May 27, 1998

/S/ RICHARD C. NOTEBAERT
----------------------
(Richard C. Notebaert)             Director                         May 27, 1998

/S/ DONALD S. PERKINS
----------------------
(Donald S. Perkins)                Director                         May 27, 1998

/S/ JOHN W. ROGERS, JR.
----------------------
(John W. Rogers, Jr.)              Director                         May 27, 1998

/S/ GEORGE A. SCHAEFER
----------------------
(George A. Schaefer)               Director                         May 27, 1998

                                      II-6
/S/ RAYMOND I. SKILLING
----------------------
(Raymond I. Skilling)              Director                         May 27, 1998

/S/ FRED L. TURNER
----------------------
(Fred L. Turner)                   Director                         May 27, 1998

/S/ ARNOLD R. WEBER
----------------------
(Arnold R. Weber)                  Director                         May 27, 1998

----------------------
(Carolyn Y. Woo)                   Director                       ________, 1998

/S/ HARVEY N. MEDVIN
----------------------
(Harvey N. Medvin)                 Executive Vice President and     May 27, 1998
                                   Chief Financial Officer (Principal
                                   Financial and Accounting Officer)

                                      II-7
EXHIBIT INDEX

EXHIBIT NO.        DESCRIPTION

4.1            Second Restated  Certificate of  Incorporation  of
               the  Registrant  --incorporated  by  reference  to
               Exhibit 3(a) to the Registrant's  Annual Report on
               Form 10-K for the year ended December 31, 1991.

4.2            Certificate  of  Amendment  of  the   Registrant's
               Second Restated  Certificate of  Incorporation  --
               incorporated  by  reference  to  Exhibit  4 to the
               Registrant's Quarterly Report on Form 10-Q for the
               quarter ending March 31, 1994.

4.3            Bylaws  of  the  Registrant  --   incorporated  by
               referenced  to  Exhibit  (d) to  the  Registrant's
               Annual  Report  on Form  10-K for the  year  ended
               December 31, 1982.

4.4            Aon Stock  Award  Plan (as  amended  and  restated
               through  1997) --  incorporated  by  reference  to
               Exhibit 10(b) to the Registrant's Quarterly Report
               on Form 10-Q for the quarter ended March 31, 1997.

4.5            Aon Stock  Option Plan (as  amended  and  restated
               through 1997) incorporated by reference to Exhibit
               10(a) to the Registrant's Quarterly Report on Form
               10-Q for the quarter ended March 31, 1997.

4.6            Aon   1998   Employee   Stock   Purchase   Plan  -
               incorporated  by  reference  to  Exhibit 10 to the
               Registrant's Quarterly Report on Form 10-Q for the
               quarter ended March 31, 1998.

4.7            Rath & Strong, Inc. Employees' Stock Bonus Plan.

5              Opinion of Jerome S. Hanner, Senior Counsel of the
               Registrant.

15             Acknowledgment of Ernst & Young LLP.

23.1           Consent of Ernst & Young LLP.

23.2           Consent  of Jerome  S.  Hanner  (contained  in the
               opinion  filed as  Exhibit  5 to the  registration
               statement).

                              II-8