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                                                                    EXHIBIT 4(b)

                                                                  EXECUTION COPY

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                          REGISTRATION RIGHTS AGREEMENT


                             Dated December 16, 2002

                                     between

                                 AON CORPORATION

                                       and

                            SALOMON SMITH BARNEY INC.

                     CREDIT SUISSE FIRST BOSTON CORPORATION

                            BNY CAPITAL MARKETS, INC.

                                       and

                            WACHOVIA SECURITIES, INC.

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                          REGISTRATION RIGHTS AGREEMENT

     THIS REGISTRATION RIGHTS AGREEMENT (the "AGREEMENT") is made and entered
into on December 16, 2002 between Corporation, a Delaware corporation (the
"COMPANY"), and Salomon Smith Barney Inc., Credit Suisse First Boston
Corporation, BNY Capital Markets, Inc. and Wachovia Securities, Inc. (the
"PURCHASERS").

     This Agreement is made pursuant to the Purchase Agreement dated
December 11, 2002 between the Company and the Purchasers (the "PURCHASE
AGREEMENT"), which provides for the sale by the Company to the Purchasers of
$225,000,000 aggregate principal amount of the Company's 7.375% Senior Notes due
2012 (the "SECURITIES"). In order to induce the Purchasers to enter into the
Purchase Agreement, the Company has agreed to provide to the Purchasers and
their direct and indirect transferees the registration rights set forth in this
Agreement. The execution of this Agreement is a condition to the closing under
the Purchase Agreement.

     In consideration of the foregoing, the parties hereto agree as follows:

      1. DEFINITIONS

     As used in this Agreement, the following capitalized defined terms shall
have the following meanings:

     "1933 ACT" shall mean the Securities Act of 1933, as amended from time to
time.

     "1934 ACT" shall mean the Securities Exchange Act of 1934, as amended from
time to time.

     "CLOSING DATE" shall mean the Closing Date as defined in the Purchase
Agreement.

     "COMPANY" shall have the meaning set forth in the preamble and shall also
include the Company's successors.

     "EXCHANGE OFFER" shall mean the exchange offer by the Company of Exchange
Securities for Registrable Securities pursuant to Section 2(a) hereof.

     "EXCHANGE OFFER REGISTRATION" shall mean a registration under the 1933 Act
effected pursuant to Section 2(a) hereof.

     "EXCHANGE OFFER REGISTRATION STATEMENT" shall mean an exchange offer

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registration statement on Form S-4 (or, if applicable, on another appropriate
form) under the 1933 Act and all amendments and supplements to such registration
statement, in each case including the Prospectus contained therein, all exhibits
thereto and all material incorporated by reference therein.

     "EXCHANGE SECURITIES" shall mean securities issued by the Company under the
Indenture containing terms identical to the Securities (except that (i) interest
thereon shall accrue from the last date on which interest was paid on the
Securities or, if no such interest has been paid, from December 16, 2002 and
(ii) the Exchange Securities generally will not contain restrictions on
transfer) and to be offered to Holders of Securities in exchange for Securities
pursuant to the Exchange Offer.

     "HOLDER" shall mean each Purchaser, for so long as it owns any Registrable
Securities, and each of its successors, assigns and direct and indirect
transferees who become registered owners of Registrable Securities under the
Indenture.

     "INDENTURE" shall mean the Indenture relating to the Securities dated as of
December 16, 2002 between the Company and The Bank of New York, as trustee, and
as the same may be amended from time to time in accordance with the terms
thereof.

     "MAJORITY HOLDERS" shall mean the Holders of a majority of the aggregate
principal amount of outstanding Registrable Securities; provided that, whenever
the consent or approval of Holders of a specified percentage of Registrable
Securities is required hereunder, Registrable Securities held by the Company or
any of its affiliates (as such term is defined in Rule 405 under the 1933 Act)
(other than the Purchasers or subsequent Holders of Registrable Securities if
such subsequent Holders are deemed to be such affiliates solely by reason of
their holding of such Registrable Securities) shall not be counted in
determining whether such consent or approval was given by the Holders of such
required percentage or amount.

     "PARTICIPATING BROKER-DEALER" shall have the meaning set forth in
Section 4(a).

     "PERSON" shall mean an individual, partnership, limited liability company,
corporation, trust or unincorporated organization, or a government or agency or
political subdivision thereof.

     "PURCHASERS" shall have the meaning set forth in the preamble.

     "PURCHASE AGREEMENT" shall have the meaning set forth in the preamble.

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     "PROSPECTUS" shall mean the prospectus included in a Registration
Statement, including any preliminary prospectus, and any such prospectus as
amended or supplemented by any prospectus supplement, including a prospectus
supplement with respect to the terms of the offering of any portion of the
Registrable Securities covered by a Shelf Registration Statement, and by all
other amendments and supplements to such prospectus, and in each case including
all material incorporated by reference therein.

     "REGISTRABLE SECURITIES" shall mean the Securities; provided, however, that
the Securities shall cease to be Registrable Securities (i) when a Registration
Statement with respect to such Securities shall have been declared effective
under the 1933 Act and such Securities shall have been disposed of pursuant to
such Registration Statement, (ii) when such Securities have been sold to the
public pursuant to Rule 144(k) (or any similar provision then in force, but not
Rule 144A) under the 1933 Act, (iii) when such Securities shall have ceased to
be outstanding or (iv) when such Securities have been exchanged for Exchange
Securities unless, in the case of any Exchange Securities referred to in this
clause (iv), such Exchange Securities are held by Participating Broker-Dealers
(in which case such Exchange Securities will be deemed to be Registrable
Securities until such time as such Exchange Securities are sold to a purchaser
in whose hands such Exchange Securities are freely tradable in accordance with
the provisions of Section 4).

     "REGISTRATION EXPENSES" shall mean any and all expenses incident to
performance of or compliance by the Company with this Agreement, including
without limitation: (i) all SEC, stock exchange or National Association of
Securities Dealers, Inc. registration and filing fees, (ii) all fees and
expenses incurred in connection with compliance with state securities or blue
sky laws (including reasonable fees and disbursements of counsel for any
underwriters or Holders in connection with blue sky qualification of any of the
Exchange Securities or Registrable Securities), (iii) all expenses of any
Persons in preparing or assisting in preparing, word processing, printing and
distributing any Registration Statement, any Prospectus, any amendments or
supplements thereto, any underwriting agreements, securities sales agreements
and other documents relating to the performance of and compliance with this
Agreement, (iv) all rating agency fees, (v) all fees and disbursements relating
to the qualification of the Indenture under applicable securities laws, (vi) the
fees and disbursements of the Trustee and its counsel, (vii) the fees and
disbursements of counsel for the Company and, in the event the Company
determines to file a Shelf Registration Statement, the reasonable fees and
disbursements of one counsel for the Holders (which counsel shall be selected by
the Majority Holders and which counsel may also be counsel for the Purchasers)
and (viii) the fees and disbursements of the independent public accountants of
the Company, including the expenses of any special audits or "COLD COMFORT"
letters required by or incident to such performance and compliance, but
excluding fees and expenses of counsel to the

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underwriters (other than fees and expenses set forth in clause (ii) above) or
the Holders and underwriting discounts and commissions and transfer taxes, if
any, relating to the sale or disposition of Registrable Securities by a Holder.

     "REGISTRATION STATEMENT" shall mean any registration statement of the
Company that covers any of the Exchange Securities or Registrable Securities
pursuant to the provisions of this Agreement and all amendments and supplements
to any such Registration Statement, including post-effective amendments, in each
case including the Prospectus contained therein, all exhibits thereto and all
material incorporated by reference therein.

     "SEC" shall mean the Securities and Exchange Commission.

     "SHELF REGISTRATION" shall mean a registration effected pursuant to
Section 2(b) hereof.

     "SHELF REGISTRATION STATEMENT" shall mean a "SHELF" registration statement
of the Company pursuant to the provisions of Section 2(b) of this Agreement
which covers all of the Registrable Securities but no other securities unless
approved by the Holders whose Registrable Securities are covered by such Shelf
Registration Statement on an appropriate form under Rule 415 under the 1933 Act,
or any similar rule that may be adopted by the SEC, and all amendments and
supplements to such registration statement, including post-effective amendments,
in each case including the Prospectus contained therein, all exhibits thereto
and all material incorporated by reference therein.

     "TRUSTEE" shall mean the trustee with respect to the Securities under the
Indenture.

     "UNDERWRITER" shall have the meaning set forth in Section 3 hereof.

     "UNDERWRITTEN REGISTRATION" or "UNDERWRITTEN OFFERING" shall mean a
registration in which Registrable Securities are sold to an Underwriter for
reoffering to the public.

      2. REGISTRATION UNDER THE 1933 ACT.

          (a)  To the extent not prohibited by any applicable law or applicable
     interpretation of the Staff of the SEC, the Company shall use its
     reasonable best efforts to cause to be filed an Exchange Offer Registration
     Statement covering the offer by the Company to the Holders to exchange all
     of the Registrable Securities for Exchange Securities and to have such
     Registration Statement remain effective until the closing of the Exchange
     Offer. The Company shall commence the Exchange Offer promptly after the
     Exchange Offer Registration Statement has been declared effective by

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     the SEC and use its reasonable best efforts to have the Exchange Offer
     consummated not later than 60 days after such effective date. The Company
     shall commence the Exchange Offer by mailing the related exchange offer
     Prospectus and accompanying documents to each Holder stating, in addition
     to such other disclosures as are required by applicable law:

               (i)    that the Exchange Offer is being made pursuant to this
          Agreement and that all Registrable Securities validly tendered and not
          withdrawn will be accepted for exchange;

               (ii)   the dates of acceptance for exchange (which shall be a
          period of at least 20 business days from the date such notice is
          mailed) (the "EXCHANGE DATES");

               (iii)  that any Registrable Security not tendered will remain
          outstanding and continue to accrue interest, but will not retain any
          rights under this Agreement;

               (iv)   that Holders electing to have a Registrable Security
          exchanged pursuant to the Exchange Offer will be required to surrender
          such Registrable Security, together with the enclosed letters of
          transmittal, to the institution and at the address (located in the
          Borough of Manhattan, The City of New York) specified in the notice
          prior to the close of business on the last Exchange Date; and

               (v)    that Holders will be entitled to withdraw their election,
          not later than the close of business on the last Exchange Date, by
          sending to the institution and at the address (located in the Borough
          of Manhattan, The City of New York) specified in the notice a
          telegram, telex, facsimile transmission or letter setting forth, among
          other things, the name of such Holder, the principal amount of
          Registrable Securities delivered for exchange and a statement that
          such Holder is withdrawing his election to have such Securities
          exchanged.

               As soon as practicable after the last Exchange Date, the Company
          shall:

               (i)    accept for exchange Registrable Securities or portions
          thereof validly tendered and not withdrawn pursuant to the Exchange
          Offer; and

               (ii)   deliver, or cause to be delivered, to the Trustee for
          cancellation all Registrable Securities or portions thereof so

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          accepted for exchange by the Company and issue, and cause the Trustee
          to promptly authenticate and mail to each Holder, an Exchange Security
          equal in principal amount to the principal amount of the Registrable
          Securities surrendered by such Holder.

     The Company shall use its reasonable best efforts to complete the Exchange
Offer as provided above and shall comply with the applicable requirements of the
1933 Act, the 1934 Act and other applicable laws and regulations in connection
with the Exchange Offer. The Exchange Offer shall not be subject to any
conditions, other than that the Exchange Offer does not violate applicable law
or any applicable interpretation of the Staff of the SEC. The Company shall
inform the Purchasers of the names and addresses of the Holders to whom the
Exchange Offer is made, and the Purchasers shall have the right, subject to
applicable law, to contact such Holders and otherwise facilitate the tender of
Registrable Securities in the Exchange Offer.

          (b)  In the event that (i) the Company determines that the Exchange
     Offer Registration provided for in Section 2(a) above is not available or
     may not be consummated as soon as practicable after the last Exchange Date
     because it would violate applicable law or the applicable interpretations
     of the Staff of the SEC or (ii) the Exchange Offer has been completed and
     in the opinion of counsel for the Purchasers a Registration Statement must
     be filed and a Prospectus must be delivered by any Purchaser in connection
     with any offering or sale of Registrable Securities, the Company may cause
     to be filed after such determination or notice of such opinion of counsel
     is given to the Company, as the case may be, a Shelf Registration Statement
     providing for the sale by the Holders of all of the Registrable Securities
     and to have such Shelf Registration Statement declared effective by the
     SEC. In the event the Company files a Shelf Registration Statement solely
     as a result of the matters referred to in clause (ii) of the preceding
     sentence, the Company shall use its reasonable best efforts to file and
     have declared effective by the SEC both an Exchange Offer Registration
     Statement pursuant to Section 2(a) with respect to all Registrable
     Securities and a Shelf Registration Statement (which may be a combined
     Registration Statement with the Exchange Offer Registration Statement) with
     respect to offers and sales of Registrable Securities held by the
     Purchasers after completion of the Exchange Offer. If the Company has
     determined to file and use its reasonable best efforts to have the Shelf
     Registration Statement declared effective, the Company agrees to use its
     reasonable best efforts to keep the Shelf Registration Statement
     continuously effective until the expiration of the period referred to in
     Rule 144(k) with respect to the Registrable Securities or such shorter
     period that will terminate when all of the Registrable Securities covered
     by the Shelf Registration Statement have been sold pursuant to the Shelf
     Registration Statement. The Company further agrees to supplement or amend
     the Shelf

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     Registration Statement if required by the rules, regulations or
     instructions applicable to the registration form used by the Company for
     such Shelf Registration Statement or by the 1933 Act or by any other rules
     and regulations thereunder for shelf registration or if reasonably
     requested by a Holder with respect to information relating to such Holder,
     and to use its reasonable best efforts to cause any such amendment to
     become effective and such Shelf Registration Statement to become usable as
     soon as thereafter practicable. The Company agrees to furnish to the
     Holders of Registrable Securities copies of any such supplement or
     amendment promptly after its being used or filed with the SEC.

          (c)  The Company shall pay all Registration Expenses in connection
     with the registration pursuant to Section 2(a) and Section 2(b). Each
     Holder shall pay all underwriting discounts and commissions and transfer
     taxes, if any, relating to the sale or disposition of such Holder's
     Registrable Securities pursuant to the Shelf Registration Statement.

          (d)  An Exchange Offer Registration Statement pursuant to Section 2(a)
     hereof or a Shelf Registration Statement pursuant to Section 2(b) hereof
     will not be deemed to have become effective unless it has been declared
     effective by the SEC; provided, however, that, if, after it has been
     declared effective, the offering of Registrable Securities pursuant to a
     Shelf Registration Statement is interfered with by any stop order,
     injunction or other order or requirement of the SEC or any other
     governmental agency or court, such Registration Statement will be deemed
     not to have become effective during the period of such interference until
     the offering of Registrable Securities pursuant to such Registration
     Statement may legally resume. In the event the Exchange Offer is not
     consummated and the Shelf Registration Statement is not declared effective
     on or prior to July 14, 2003, the interest rate on the Securities will be
     increased by 0.5% per annum until (i) the Exchange Offer is consummated,
     (ii) the Shelf Registration Statement is declared effective by the SEC, or
     (iii) the Securities shall have ceased to be outstanding.

          (e)  Without limiting the remedies available to the Purchasers and the
     Holders, the Company acknowledges that any failure by the Company to comply
     with its obligations under Section 2(a) and Section 2(b) hereof may result
     in material irreparable injury to the Purchasers or the Holders for which
     there is no adequate remedy at law, that it will not be possible to measure
     damages for such injuries precisely and that, in the event of any such
     failure, the Purchasers or any Holder may obtain such relief as may be
     required to specifically enforce the Company's obligations under
     Section 2(a) and Section 2(b) hereof.

      3. REGISTRATION PROCEDURES.

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     In connection with the obligations of the Company with respect to the
Registration Statements pursuant to Section 2(a) and Section 2(b) (if the
Company has determined to file a Shelf Registration Statement and use its
reasonable best efforts to have such Shelf Registration Statement declared
effective) hereof, the Company shall as expeditiously as possible:

          (a)  prepare and file with the SEC a Registration Statement on the
     appropriate form under the 1933 Act, which form (x) shall be selected by
     the Company and (y) shall, in the case of a Shelf Registration, be
     available for the sale of the Registrable Securities by the selling Holders
     thereof and (z) shall comply as to form in all material respects with the
     requirements of the applicable form and include all financial statements
     required by the SEC to be filed therewith, and use its reasonable best
     efforts to have such Registration Statement become effective and remain
     effective in accordance with Section 2 hereof;

          (b)  prepare and file with the SEC such amendments and post-effective
     amendments to each Registration Statement as may be necessary to keep such
     Registration Statement effective for the applicable period and cause each
     Prospectus to be supplemented by any required prospectus supplement and, as
     so supplemented, to be filed pursuant to Rule 424 under the 1933 Act;

          (c)  in the case of a Shelf Registration, furnish to each Holder of
     Registrable Securities, to counsel for the Purchasers, to counsel for the
     Holders and to each Underwriter of an Underwritten Offering of Registrable
     Securities, if any, without charge, as many copies of each Prospectus,
     including each preliminary Prospectus, and any amendment or supplement
     thereto and such other documents as such Holder or Underwriter may
     reasonably request, in order to facilitate the public sale or other
     disposition of the Registrable Securities; and the Company consents to the
     use of such Prospectus and any amendment or supplement thereto in
     accordance with applicable law by each of the selling Holders of
     Registrable Securities and any such Underwriters in connection with the
     offering and sale of the Registrable Securities covered by and in the
     manner described in such Prospectus or any amendment or supplement thereto
     in accordance with applicable law;

          (d)  use its reasonable best efforts to register or qualify the
     Registrable Securities under all applicable state securities or "BLUE SKY"
     laws of such jurisdictions as any Holder of Registrable Securities covered
     by a Registration Statement shall reasonably request in writing by the time
     the applicable Registration Statement is declared effective by the SEC, to
     cooperate with such Holders in connection with any filings required to be

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     made with the National Association of Securities Dealers, Inc. and do any
     and all other acts and things which may be reasonably necessary or
     advisable to enable such Holder to consummate the disposition in each such
     jurisdiction of such Registrable Securities owned by such Holder; provided,
     however, that the Company shall not be required to (i) qualify as a foreign
     corporation or as a dealer in securities in any jurisdiction where it would
     not otherwise be required to qualify but for this Section 3(d), (ii) file
     any general consent to service of process or (iii) subject itself to
     taxation in any such jurisdiction if it is not so subject;

          (e)  in the case of a Shelf Registration, notify each Holder of
     Registrable Securities, counsel for the Holders and counsel for the
     Purchasers promptly and, if requested by any such Holder or counsel,
     confirm such advice in writing (i) when a Registration Statement has become
     effective and when any post-effective amendment thereto has been filed and
     becomes effective, (ii) of any request by the SEC or any state securities
     authority for amendments and supplements to a Registration Statement and
     Prospectus or for additional information after the Registration Statement
     has become effective, (iii) of the issuance by the SEC or any state
     securities authority of any stop order suspending the effectiveness of a
     Registration Statement or the initiation of any proceedings for that
     purpose, (iv) if, between the effective date of a Registration Statement
     and the closing of any sale of Registrable Securities covered thereby, the
     representations and warranties of the Company contained in any underwriting
     agreement, securities sales agreement or other similar agreement, if any,
     relating to the offering cease to be true and correct in all material
     respects or if the Company receives any notification with respect to the
     suspension of the qualification of the Registrable Securities for sale in
     any jurisdiction or the initiation of any proceeding for such purpose, (v)
     of the happening of any event during the period a Shelf Registration
     Statement is effective which makes any statement made in such Registration
     Statement or the related Prospectus untrue in any material respect or which
     requires the making of any changes in such Registration Statement or
     Prospectus in order to make the statements therein not misleading and (vi)
     of any determination by the Company that a post-effective amendment to a
     Registration Statement would be appropriate;

          (f)  make every reasonable effort to obtain the withdrawal of any
     order suspending the effectiveness of a Registration Statement at the
     earliest possible moment and provide immediate notice to each Holder of the
     withdrawal of any such order;

          (g)  in the case of a Shelf Registration, furnish to each Holder of
     Registrable Securities, without charge, at least one conformed copy of

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     each Registration Statement and any post-effective amendment thereto
     (without documents incorporated therein by reference or exhibits thereto,
     unless requested), unless such documents are available on the SEC's EDGAR
     Website;

          (h)  in the case of a Shelf Registration, cooperate with the selling
     Holders of Registrable Securities to facilitate the timely preparation and
     delivery of certificates representing Registrable Securities to be sold and
     not bearing any restrictive legends and enable such Registrable Securities
     to be in such denominations (consistent with the provisions of the
     Indenture) and registered in such names as the selling Holders may
     reasonably request at least one business day prior to the closing of any
     sale of Registrable Securities;

          (i)  in the case of a Shelf Registration, upon the occurrence of any
     event contemplated by Section 3(e)(v) hereof, use its reasonable best
     efforts to prepare and file with the SEC a supplement or post-effective
     amendment to a Registration Statement or the related Prospectus or any
     document incorporated therein by reference or file any other required
     document so that, as thereafter delivered to the purchasers of the
     Registrable Securities, such Prospectus will not contain any untrue
     statement of a material fact or omit to state a material fact necessary to
     make the statements therein, in light of the circumstances under which they
     were made, not misleading. The Company agrees to notify the Holders to
     suspend use of the Prospectus as promptly as practicable after the
     occurrence of such an event, and the Holders hereby agree to suspend use of
     the Prospectus until the Company has amended or supplemented the Prospectus
     to correct such misstatement or omission;

          (j)  a reasonable time prior to the filing of any Registration
     Statement, any Prospectus, any amendment to a Registration Statement or
     amendment or supplement to a Prospectus or any document which is to be
     incorporated by reference into a Registration Statement or a Prospectus
     after the initial filing of a Registration Statement, provide the
     Purchasers and its counsel (and, in the case of a Shelf Registration
     Statement, the counsel to the Holders) a reasonable opportunity to comment
     on such document;

          (k)  obtain a CUSIP number for all Exchange Securities or Registrable
     Securities, as the case may be, not later than the effective date of a
     Registration Statement;

          (l)  cause the Indenture to be qualified under the Trust Indenture Act
     of 1939, as amended (the "TIA"), in connection with the registration of the
     Exchange Securities or Registrable Securities, as the case may be,

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     cooperate with the Trustee and the Holders to effect such changes to the
     Indenture as may be required for the Indenture to be so qualified in
     accordance with the terms of the TIA and execute, and use its reasonable
     best efforts to cause the Trustee to execute, all documents as may be
     required to effect such changes and all other forms and documents required
     to be filed with the SEC to enable the Indenture to be so qualified in a
     timely manner;

          (m)  in the case of a Shelf Registration, make available for
     inspection by the Holders of the Registrable Securities, any Underwriter
     participating in any disposition pursuant to such Shelf Registration
     Statement, and attorneys and accountants designated by the Holders, at
     reasonable times and in a reasonable manner, all financial and other
     records, pertinent documents and properties of the Company, and cause the
     respective officers, directors and employees of the Company to supply all
     information reasonably requested by any such representative, Underwriter,
     attorney or accountant in connection with a Shelf Registration Statement;
     provided, however, that the foregoing inspection and gathering of
     information shall be coordinated, on behalf of any Underwriter, by such
     Underwriter and, on behalf of the other parties, by one counsel designated
     by and on behalf of such other parties; and provided further that such
     persons shall first agree in writing with the Company that any information
     that is reasonably and in good faith designated by the Company as
     confidential at the time of delivery of such information shall be kept
     confidential by such persons unless (i) disclosure of such information is
     required by court or administrative order or is necessary to respond to
     inquiries of regulatory authorities, (ii) disclosure of such information is
     required by law (including any disclosure requirements pursuant to Federal
     securities laws in connection with the filing of the Shelf Registration
     Statement or the use of any Prospectus thereunder), (iii) such information
     becomes generally available to the public other than as a result of
     disclosure, directly or indirectly, or failure to safeguard by any such
     person, or (iv) such information becomes available to any such person on a
     non-confidential basis from a source other than the Company and such source
     is not bound by a confidentiality agreement or other obligation not to
     disclose such information;

          (n)  in the case of a Shelf Registration, use its reasonable best
     efforts to cause all Registrable Securities to be listed on any securities
     exchange or any automated quotation system on which similar securities
     issued by the Company are then listed if requested by the Majority Holders,
     to the extent such Registrable Securities satisfy applicable listing
     requirements;

          (o)  use its reasonable best efforts to cause the Exchange

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     Securities or Registrable Securities, as the case may be, to be rated by
     two nationally recognized statistical rating organizations (as such term is
     defined in Rule 436(g)(2) under the 1933 Act);

          (p)  if reasonably requested by any Holder of Registrable Securities
     covered by a Registration Statement, (i) promptly incorporate in a
     Prospectus supplement or post-effective amendment such information with
     respect to such Holder as such Holder reasonably requests to be included
     therein and (ii) make all required filings of such Prospectus supplement or
     such post-effective amendment as soon as the Company has received
     notification of the matters to be incorporated in such filing; and

          (q)  in the case of a Shelf Registration, use its reasonable best
     efforts to enter into such customary agreements and take all such other
     actions in connection therewith (including those requested by the Holders
     of a majority of the Registrable Securities being sold) in order to
     expedite or facilitate the disposition of such Registrable Securities in an
     Underwritten Offering and in such connection, (i) to the extent possible,
     make such representations and warranties to the Holders and any
     Underwriters of such Registrable Securities with respect to the business of
     the Company and its subsidiaries, the Registration Statement, Prospectus
     and documents incorporated by reference or deemed incorporated by
     reference, if any, in each case, in form, substance and scope as are
     customarily made by issuers to underwriters in underwritten offerings, (ii)
     obtain opinions of counsel to the Company (which counsel and opinions, in
     form, scope and substance, shall be reasonably satisfactory to the Holders
     and such Underwriters and their respective counsel) addressed to each
     selling Holder and Underwriter of Registrable Securities, covering the
     matters customarily covered in opinions requested in underwritten
     offerings, (iii) obtain "COLD COMFORT" letters from the independent
     certified public accountants of the Company (and, if necessary, any other
     certified public accountant of any subsidiary of the Company, or of any
     business acquired by the Company for which financial statements and
     financial data are or are required to be included in the Registration
     Statement) addressed to each selling Holder and Underwriter of Registrable
     Securities, such letters to be in customary form and covering matters of
     the type customarily covered in "COLD COMFORT" letters in connection with
     underwritten offerings, and (iv) deliver such documents and certificates as
     may be reasonably requested by the Holders of a majority in principal
     amount of the Registrable Securities being sold or the Underwriters, and
     which are customarily delivered in underwritten offerings, to evidence the
     continued validity of the representations and warranties of the Company
     made pursuant to clause (i) above and to evidence compliance with any
     customary conditions contained in an underwriting agreement.

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     In the case of a Shelf Registration Statement, the Company may require each
Holder of Registrable Securities to furnish to the Company such information
regarding the Holder and the proposed distribution by such Holder of such
Registrable Securities as the Company may from time to time reasonably request
in writing. Each Holder agrees to provide such information to the Company.

     In the case of a Shelf Registration Statement, each Holder agrees that,
upon receipt of any notice from the Company of the happening of any event of the
kind described in Section 3(e)(v) hereof, such Holder will forthwith discontinue
disposition of Registrable Securities pursuant to a Registration Statement until
such Holder's receipt of the copies of the supplemented or amended Prospectus
contemplated by Section 3(i) hereof, and, if so directed by the Company, such
Holder will deliver to the Company (at its expense) all copies in its
possession, other than permanent file copies then in such Holder's possession,
of the Prospectus covering such Registrable Securities current at the time of
receipt of such notice. If the Company shall give any such notice to suspend the
disposition of Registrable Securities pursuant to a Registration Statement, the
Company shall extend the period during which the Registration Statement shall be
maintained effective pursuant to this Agreement by the number of days during the
period from and including the date of the giving of such notice to and including
the date when the Holders shall have received copies of the supplemented or
amended Prospectus necessary to resume such dispositions and any such
suspensions may not exceed 90 days in the aggregate during any 365 day period.

     The Holders of Registrable Securities covered by a Shelf Registration
Statement who desire to do so may sell such Registrable Securities in an
Underwritten Offering. In any such Underwritten Offering, the investment banker
or investment bankers and manager or managers (the "UNDERWRITERS") that will
administer the offering will be selected by the Majority Holders of the
Registrable Securities included in such offering.

      4. PARTICIPATION OF BROKER-DEALERS IN EXCHANGE OFFER.

          (a)  The parties hereto understand that the Staff of the SEC has taken
     the position that any broker-dealer that receives Exchange Securities for
     its own account in the Exchange Offer in exchange for Securities that were
     acquired by such broker-dealer as a result of market-making or other
     trading activities (a "Participating Broker-Dealer"), may be deemed to be
     an "underwriter" within the meaning of the 1933 Act and must deliver a
     prospectus meeting the requirements of the 1933 Act in connection with any
     resale of such Exchange Securities.

     The Company understands that it is currently the Staff's position that if
the Prospectus contained in the Exchange Offer Registration Statement includes a
plan of distribution containing a statement to the above effect and the means by

                                       13
<Page>

which Participating Broker-Dealers may resell the Exchange Securities, without
naming the Participating Broker-Dealers or specifying the amount of Exchange
Securities owned by them, such Prospectus may be delivered by Participating
Broker-Dealers to satisfy their prospectus delivery obligation under the 1933
Act in connection with resales of Exchange Securities for their own accounts, so
long as the Prospectus otherwise meets the requirements of the 1933 Act.

          (b)  In light of the above, notwithstanding the other provisions of
     this Agreement, the Company agrees that the provisions of this Agreement as
     they relate to a Shelf Registration shall also apply to an Exchange Offer
     Registration to the extent, and with such reasonable modifications thereto,
     as may be reasonably requested by the Purchasers or by one or more
     Participating Broker-Dealers, in each case as provided in clause (ii)
     below, in order to expedite or facilitate the disposition of any Exchange
     Securities by Participating Broker-Dealers consistent with the positions of
     the Staff recited in Section 4(a) above; PROVIDED that:

               (i)    the Company shall not be required to amend or supplement
          the Prospectus contained in the Exchange Offer Registration Statement,
          as would otherwise be contemplated by Section 3(i), for a period
          exceeding 180 days after the last Exchange Date (as such period may be
          extended pursuant to the penultimate paragraph of Section 3 of this
          Agreement) and Participating Broker-Dealers shall not be authorized by
          the Company to deliver and shall not deliver such Prospectus after
          such period in connection with the resales contemplated by this
          Section 4; and

               (ii)   the application of the Shelf Registration procedures set
          forth in Section 3 of this Agreement to an Exchange Offer
          Registration, to the extent not required by the positions of the Staff
          of the SEC or the 1933 Act and the rules and regulations thereunder,
          will be in conformity with the reasonable request in writing to the
          Company by the Purchasers or with the reasonable request in writing to
          the Company by one or more broker-dealers who certify to the
          Purchasers and the Company in writing that they anticipate that they
          will be Participating Broker-Dealers; and PROVIDED FURTHER that, in
          connection with such application of the Shelf Registration procedures
          set forth in Section 3 to an Exchange Offer Registration, the Company
          shall be obligated (x) to deal only with one entity representing the
          Participating Broker-Dealers, which shall be Salomon Smith Barney Inc.
          unless it elects not to act as such representative, (y) to pay the
          fees and expenses of only one counsel representing the Participating
          Broker-Dealers, which shall be counsel to the Purchasers unless such
          counsel elects not to

                                       14
<Page>

          so act and (z) to cause to be delivered only one, if any, "cold
          comfort" letter with respect to the Prospectus in the form existing on
          the last Exchange Date and with respect to each subsequent amendment
          or supplement, if any, effected during the period specified in clause
          (i) above.

     For purposes of this Section 4(b), all references in Section 3 to the
"Majority Holders" shall be deemed to mean, solely insofar as relates to this
Section 4(b), the Participating Broker-Dealers who are the Holders of the
majority in aggregate principal amount of the Exchange Securities which are
Registrable Securities

          (c)  The Purchasers shall have no liability to the Company, other than
     as Holders in accordance with the terms hereof, or to any other Holder with
     respect to any request that they may make pursuant to Section 4(b) above.

      5. INDEMNIFICATION AND CONTRIBUTION.

          (a)  The Company agrees to indemnify and hold harmless each Purchaser,
     each Holder and each Person, if any, who controls any Purchaser or any such
     Holder within the meaning of either Section 15 of the 1933 Act or Section
     20 of the 1934 Act, from and against all losses, claims, damages and
     liabilities (including, without limitation, any legal or other expenses
     reasonably incurred in connection with defending or investigating any such
     action or claim) caused by any untrue statement or alleged untrue statement
     of a material fact contained in any Registration Statement (or any
     amendment thereto) pursuant to which Exchange Securities or Registrable
     Securities were registered under the 1933 Act, including all documents
     incorporated therein by reference, or caused by any omission or alleged
     omission to state a material fact required to be stated therein or
     necessary to make the statements therein not misleading, or caused by any
     untrue statement or alleged untrue statement of a material fact contained
     in any Prospectus (as amended or supplemented if the Company shall have
     furnished any amendments or supplements thereto), or caused by any omission
     or alleged omission to state a material fact necessary to make the
     statements therein in light of the circumstances under which they were made
     not misleading, except insofar as such losses, claims, damages or
     liabilities are caused by any such untrue statement or omission or alleged
     untrue statement or omission based upon information relating to any
     Purchaser or any Holder furnished to the Company in writing by such
     Purchaser or any selling Holder expressly for use therein, provided,
     however, that the foregoing indemnity with respect to any such Registration
     Statement or Prospectus, including any document incorporated therein by
     reference, shall not inure to the benefit of any

                                       15
<Page>

     Purchaser or any Holder (or to the benefit of any Person controlling such
     Holder) from whom the Person asserting any such losses, claims, damages or
     liabilities purchased the Registrable Securities if such untrue statement
     or omission or alleged untrue statement or alleged omission made in any
     such Registration Statement or Prospectus, including any document
     incorporated therein by reference, is eliminated or remedied in an
     amendment or supplement thereto and a copy of the amended or supplemented
     Registration Statement or Prospectus has not been furnished to such person
     on or prior to the written confirmation of the sale of such Registrable
     Securities to such Person. In connection with any Underwritten Offering
     permitted by Section 3, the Company will also indemnify the Underwriters,
     if any, selling brokers, dealers and similar securities industry
     professionals participating in the distribution, their officers and
     directors and each Person who controls such Persons (within the meaning of
     the 1933 Act and the 1934 Act) to the same extent as provided above with
     respect to the indemnification of the Holders, if requested in connection
     with any Registration Statement.

          (b)  Each Holder agrees, severally and not jointly, to indemnify and
     hold harmless the Company, the Purchasers and the other selling Holders,
     and each of their respective directors, officers of the Company who sign
     the Registration Statement and each Person, if any, who controls the
     Company, the Purchasers and any other selling Holder within the meaning of
     either Section 15 of the 1933 Act or Section 20 of the 1934 Act to the same
     extent as the foregoing indemnity from the Company to the Purchasers and
     the Holders, but only with reference to information relating to such Holder
     furnished to the Company in writing by such Holder expressly for use in any
     Registration Statement (or any amendment thereto) or any Prospectus (or any
     amendment or supplement thereto).

          (c)  In case any proceeding (including any governmental investigation)
     shall be instituted involving any Person in respect of which indemnity may
     be sought pursuant to either paragraph (a) or paragraph (b) of this Section
     5, such Person (the "INDEMNIFIED PARTY") shall promptly notify the Person
     against whom such indemnity may be sought (the "INDEMNIFYING PARTY") in
     writing and the indemnifying party, upon request of the indemnified party,
     shall retain counsel reasonably satisfactory to the indemnified party to
     represent the indemnified party and any others the indemnifying party may
     designate in such proceeding and shall pay the fees and disbursements of
     such counsel related to such proceeding. In any such proceeding, any
     indemnified party shall have the right to retain its own counsel, but the
     fees and expenses of such counsel shall be at the expense of such
     indemnified party unless (i) the indemnifying party and the indemnified
     party shall have mutually agreed to the retention of such counsel or (ii)
     the named parties to any such

                                       16
<Page>

     proceeding (including any impleaded parties) include both the indemnifying
     party and the indemnified party and representation of both parties by the
     same counsel would be inappropriate due to actual or potential differing
     interests between them. It is understood that the indemnifying party shall
     not, in connection with any proceeding or related proceedings in the same
     jurisdiction, be liable for (A) the fees and expenses of more than one
     separate firm (in addition to any local counsel) for the Purchasers and all
     Persons, if any, who control any Purchaser within the meaning of either
     Section 15 of the 1933 Act or Section 20 of the 1934 Act, (B) the fees and
     expenses of more than one separate firm (in addition to any local counsel)
     for the Company, its directors, its officers who sign the Registration
     Statement and each Person, if any, who controls the Company within the
     meaning of either such Section and (C) the fees and expenses of more than
     one separate firm (in addition to any local counsel) for all Holders and
     all Persons, if any, who control any Holders within the meaning of either
     such Section, and that all such fees and expenses shall be reimbursed as
     they are incurred. In such case involving the Purchasers and Persons who
     control any Purchaser, such firm shall be designated in writing by such
     Purchaser. In such case involving the Holders and such Persons who control
     any Holder, such firm shall be designated in writing by the Majority
     Holders. In all other cases, such firm shall be designated by the Company.
     The indemnifying party shall not be liable for any settlement of any
     proceeding effected without its written consent but, if settled with such
     consent or if there be a final judgment for the plaintiff, the indemnifying
     party agrees to indemnify the indemnified party from and against any loss
     or liability by reason of such settlement or judgment. Notwithstanding the
     foregoing sentence, if at any time an indemnified party shall have
     requested an indemnifying party to reimburse the indemnified party for fees
     and expenses of counsel as contemplated by the second and third sentences
     of this paragraph, the indemnifying party agrees that it shall be liable
     for any settlement of any proceeding effected without its written consent
     if (i) such settlement is entered into more than 30 days after receipt by
     such indemnifying party of the aforesaid request and (ii) such indemnifying
     party shall not have reimbursed the indemnified party for such fees and
     expenses of counsel in accordance with such request prior to the date of
     such settlement. No indemnifying party shall, without the prior written
     consent of the indemnified party, effect any settlement of any pending or
     threatened proceeding in respect of which such indemnified party is or
     could have been a party and indemnity could have been sought hereunder by
     such indemnified party, unless such settlement includes an unconditional
     release of such indemnified party from all liability on claims that are the
     subject matter of such proceeding.

          (d)  If the indemnification provided for in paragraph (a) or
     paragraph (b) of this Section 5 is unavailable to an indemnified party or

                                       17
<Page>

     insufficient in respect of any losses, claims, damages or liabilities
     referred to therein, then each indemnifying party under such paragraph, in
     lieu of indemnifying such indemnified party thereunder, shall contribute to
     the amount paid or payable by such indemnified party as a result of such
     losses, claims, damages or liabilities in such proportion as is appropriate
     to reflect the relative fault of the indemnifying party or parties on the
     one hand and of the indemnified party or parties on the other hand in
     connection with the statements or omissions that resulted in such losses,
     claims, damages or liabilities, as well as any other relevant
     considerations. The relative fault of the Company, the Holders and the
     Underwriters, if any, shall be determined by reference to, among other
     things, whether the untrue or alleged untrue statement of a material fact
     or the omission or alleged omission to state a material fact relates to
     information supplied by the Company or by the Holders or the Underwriters,
     if any, and the parties' relative intent, knowledge, access to information
     and opportunity to correct or prevent such statement or omission. The
     Holders' respective obligations to contribute pursuant to this Section 5(d)
     are several in proportion to the respective principal amount of Registrable
     Securities of such Holder that were registered pursuant to a Registration
     Statement.

          (e)  The Company and each Holder agree that it would not be just or
     equitable if contribution pursuant to this Section 5 were determined by pro
     rata allocation or by any other method of allocation that does not take
     account of the equitable considerations referred to in paragraph (d) above.
     The amount paid or payable by an indemnified party as a result of the
     losses, claims, damages and liabilities referred to in paragraph (d) above
     shall be deemed to include, subject to the limitations set forth above, any
     legal or other expenses reasonably incurred by such indemnified party in
     connection with investigating or defending any such action or claim.
     Notwithstanding the provisions of this Section 5, no Holder shall be
     required to indemnify or contribute any amount in excess of the amount by
     which the total price at which Registrable Securities were sold by such
     Holder exceeds the amount of any damages that such Holder has otherwise
     been required to pay by reason of such untrue or alleged untrue statement
     or omission or alleged omission. No Person guilty of fraudulent
     misrepresentation (within the meaning of Section 11(f) of the 1933 Act)
     shall be entitled to contribution from any Person who was not guilty of
     such fraudulent misrepresentation. The remedies provided for in this
     Section 5 are not exclusive and shall not limit any rights or remedies
     which may otherwise be available to any indemnified party at law or in
     equity.

     The indemnity and contribution provisions contained in this Section 5 shall
remain operative and in full force and effect regardless of (i) any termination
of this Agreement, (ii) any investigation made by or on behalf of the
Purchasers,

                                       18
<Page>

any Holder or any Person controlling any Purchaser or any Holder, or by or on
behalf of the Company, its officers or directors or any Person controlling the
Company, (iii) acceptance of any of the Exchange Securities and (iv) any sale of
Registrable Securities pursuant to a Shelf Registration Statement.

      6. MISCELLANEOUS.

          (a)  No Inconsistent Agreements. The Company has not entered into, and
     on or after the date of this Agreement will not enter into, any agreement
     which breaches the rights granted to the Holders of Registrable Securities
     in this Agreement or the provisions hereof. The rights granted to the
     Holders hereunder do not breach the rights granted to the holders of the
     Company's other issued and outstanding securities under any such
     agreements.

          (b)  Amendments and Waivers. The provisions of this Agreement,
     including the provisions of this sentence, may not be amended, modified or
     supplemented, and waivers or consents to departures from the provisions
     hereof may not be given unless the Company has obtained the written consent
     of Holders of at least a majority in aggregate principal amount of the
     outstanding Registrable Securities affected by such amendment,
     modification, supplement, waiver or consent; provided, however, that no
     amendment, modification, supplement, waiver or consent to any departure
     from the provisions of Section 5 hereof shall be effective as against any
     Holder of Registrable Securities unless consented to in writing by such
     Holder.

          (c)  Notices. All notices and other communications provided for or
     permitted hereunder shall be made in writing by hand-delivery, registered
     first-class mail, telex, telecopier, or any courier guaranteeing overnight
     delivery (i) if to a Holder, at the most current address given by such
     Holder to the Company by means of a notice given in accordance with the
     provisions of this Section 6(c), which address initially is, the address of
     the representatives of the Purchasers set forth in the Purchase Agreement;
     and (ii) if to the Company, initially at the Company's address set forth in
     the Purchase Agreement and thereafter at such other address, notice of
     which is given in accordance with the provisions of this Section 6(c).

     All such notices and communications shall be deemed to have been duly
given: at the time delivered by hand, if personally delivered; five business
days after being deposited in the mail, postage prepaid, if mailed; when
answered back, if telexed; when receipt is acknowledged, if telecopied; and on
the next business day if timely delivered to an air courier guaranteeing
overnight delivery.

                                       19
<Page>

     Copies of all such notices, demands, or other communications shall be
concurrently delivered by the Person giving the same to the Trustee, at the
address specified in the Indenture.

          (d)  Successors and Assigns. This Agreement shall inure to the benefit
     of and be binding upon the successors, assigns and transferees of each of
     the parties, including, without limitation and without the need for an
     express assignment, subsequent Holders; provided that nothing herein shall
     be deemed to permit any assignment, transfer or other disposition of
     Registrable Securities in violation of the terms of the Purchase Agreement.
     If any transferee of any Holder shall acquire Registrable Securities, in
     any manner, whether by operation of law or otherwise, such Registrable
     Securities shall be held subject to all of the terms of this Agreement, and
     by taking and holding such Registrable Securities such Person shall be
     conclusively deemed to have agreed to be bound by and to perform all of the
     terms and provisions of this Agreement and such Person shall be entitled to
     receive the benefits hereof. Each Purchaser (in its capacity as Purchaser)
     shall have no liability or obligation to the Company with respect to any
     failure by a Holder to comply with, or any breach by any Holder of, any of
     the obligations of such Holder under this Agreement.

          (e)  Purchases and Sales of Securities. The Company shall not, and
     shall use its reasonable best efforts to cause its affiliates (as defined
     in Rule 405 under the 1933 Act) not to, purchase and then resell or
     otherwise transfer any Securities (other than to another affiliate of the
     Company).

          (f)  Third Party Beneficiary. The Holders shall be third party
     beneficiaries to the agreements made hereunder between the Company, on the
     one hand, and the Purchasers, on the other hand, and shall have the right
     to enforce such agreements directly to the extent it deems such enforcement
     necessary or advisable to protect its rights or the rights of Holders
     hereunder.

          (g)  Counterparts. This Agreement may be executed in any number of
     counterparts and by the parties hereto in separate counterparts, each of
     which when so executed shall be deemed to be an original and all of which
     taken together shall constitute one and the same agreement.

          (h)  Headings. The headings in this Agreement are for convenience of
     reference only and shall not limit or otherwise affect the meaning hereof.

          (i)  Governing Law. This Agreement shall be governed by the laws of
     the State of New York.

                                       20
<Page>

          (j)  Severability. In the event that any one or more of the provisions
     contained herein, or the application thereof in any circumstance, is held
     invalid, illegal or unenforceable, the validity, legality and
     enforceability of any such provision in every other respect and of the
     remaining provisions contained herein shall not be affected or impaired
     thereby.

                                       21
<Page>

     IN WITNESS WHEREOF, the parties have executed this Agreement as of the date
first written above.

                                                AON CORPORATION


                                                By: /s/ Harvey N. Medvin
                                                    ----------------------------
                                                    Name:
                                                    Title:

Confirmed and accepted as of
 the date first above written:

Salomon Smith Barney Inc.
 Credit Suisse First Boston Corporation

For themselves and on behalf of the several
purchasers named in Schedule I hereto.

SALOMON SMITH BARNEY INC.


By: /s/ Anne Kronenberg
    -------------------------------
    Name:
    Title:

CREDIT SUISSE FIRST BOSTON CORPORATION


By: /s/ Sharon Harrison
    -------------------------------
    Name:  Sharon Harrison
    Title: Director


                                       22
<Page>

                                                                      SCHEDULE I

               PURCHASER

Salomon Smith Barney Inc.

Credit Suisse First Boston Corporation

BNY Capital Markets, Inc.

Wachovia Securities, Inc.

                                       23
<Page>

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