Aon Corporation $600,000,000 3.500% Senior Notes Due 2015 $600,000,000 5.000% Senior Notes Due 2020 $300,000,000 6.250% Senior Notes Due 2040 UNDERWRITING AGREEMENT

Exhibit 1.1

EXECUTION VERSION

Aon Corporation

$600,000,000 3.500% Senior Notes Due 2015

$600,000,000 5.000% Senior Notes Due 2020

$300,000,000 6.250% Senior Notes Due 2040

UNDERWRITING AGREEMENT

September 7, 2010

CREDIT SUISSE SECURITIES (USA) LLC

MORGAN STANLEY & CO. INCORPORATED

BANC OF AMERICA SECURITIES LLC

DEUTSCHE BANK SECURITIES INC.

RBS SECURITIES INC.,

As Representatives of the Several Underwriters,

c/o Credit Suisse Securities (USA) LLC,

Eleven Madison Avenue,

New York, N.Y. 10010-3629

Dear Sirs:

1.  Introductory. Aon Corporation, a Delaware corporation (“Company”), agrees with the several Underwriters named in Schedule A hereto (“Underwriters”) to issue and sell to the several Underwriters $600,000,000 principal amount of its 3.500% Senior Notes due 2015 (“2015 Notes”), $600,000,000 principal amount of its 5.000% Senior Notes due 2020 (“2020 Notes”) and $300,000,000 principal amount of its 6.250% Senior Notes due 2040 (“2040 Notes”, and together with the 2015 Notes and the 2020 Notes, the “Offered Securities”) to be issued under an indenture, dated as of September 10, 2010, between the Company and The Bank of New York Mellon Trust Company, N.A., as Trustee, (the “Indenture”).

As part of the transactions described under the heading “Summary—Aon Corporation—Pending Merger with Hewitt” in the General Disclosure Package, the Company intends to merge with Hewitt Associates, Inc., a Delaware corporation (“Hewitt”), pursuant to an Agreement and Plan of Merger (the “Merger Agreement”), dated as of July 11, 2010, by and among the Company, Alps Merger Corp., Alps Merger LLC and Hewitt, subject to the conditions and terms of such Merger Agreement (the “Merger”).

2.  Representations and Warranties of the Company.  The Company represents and warrants to, and agrees with, the several Underwriters that:

(a)  Filing and Effectiveness of Registration Statement; Certain Defined Terms.  The Company has filed with the Commission a registration statement on Form S-3 (No. 333-159841), including a related prospectus or prospectuses, covering the registration of the Offered Securities under the Act, which has become effective.  “Registration Statement” at any particular time means such registration statement in the form then filed with the Commission, including any amendment thereto, any document incorporated by reference therein and all 430B Information and all 430C Information with respect to such registration statement, that in any case has not been superseded or modified.  “Registration Statement” without reference to a time means the Registration Statement as of the Effective Time.  For purposes of this definition, 430B Information shall be considered to be included in the Registration Statement as of the time specified in Rule 430B.

For purposes of this Agreement:

“430B Information” means information included in a prospectus then deemed to be a part of the Registration Statement pursuant to Rule 430B(e) or retroactively deemed to be a part of the Registration Statement pursuant to Rule 430B(f).

“430C Information” means information included in a prospectus then deemed to be a part of the Registration Statement pursuant to Rule 430C.

“Act” means the Securities Act of 1933, as amended.

“Applicable Time” means 6:15 p.m. (Eastern time) on the date of this Agreement.

“Closing Date” has the meaning set forth in Section 3 hereof.

“Commission” means the Securities and Exchange Commission.

“Effective Time” of the Registration Statement relating to the Offered Securities means the time of the first contract of sale for the Offered Securities.

“Exchange Act” means the Securities Exchange Act of 1934.

“Final Prospectus” means the Statutory Prospectus that discloses the public offering price, other 430B Information and other final terms of the Offered Securities, and otherwise satisfies Section 10(a) of the Act.

“General Use Issuer Free Writing Prospectus” means any Issuer Free Writing Prospectus that is intended for general distribution to prospective investors, as evidenced by its being so specified in Schedule B to this Agreement.

“Issuer Free Writing Prospectus” means any “issuer free writing prospectus,” as defined in Rule 433, relating to the Offered Securities in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained in the Company’s records pursuant to Rule 433(g).

“Limited Use Issuer Free Writing Prospectus” means any Issuer Free Writing Prospectus that is not a General Use Issuer Free Writing Prospectus.

“Rules and Regulations” means the rules and regulations of the Commission.

“Securities Laws” means, collectively, the Sarbanes-Oxley Act of 2002 (“Sarbanes-Oxley”), the Act, the Exchange Act, the Trust Indenture Act, the Rules and Regulations, the auditing principles, rules, standards and practices applicable to auditors of “issuers” (as defined in Sarbanes-Oxley) promulgated or approved by the Public Company Accounting Oversight Board and, as applicable, the rules of the New York Stock Exchange (“Exchange Rules”).

“Statutory Prospectus” with reference to any particular time means the prospectus relating to the Offered Securities that is included in the Registration Statement immediately prior to that time, including all 430B Information and all 430C Information with respect to the Registration Statement.  For purposes of the foregoing definition, 430B Information shall be considered to be included in the Statutory Prospectus only as of the actual time that such form of prospectus (including a prospectus supplement) is filed with the Commission pursuant to Rule 424(b) and not retroactively.

“Trust Indenture Act” means the Trust Indenture Act of 1939.

Unless otherwise specified, a reference to a “rule” is to the indicated rule under the Act.

(b)  Compliance with Act Requirements.  (i) (A) At the time the Registration Statement initially became effective, (B) at the time of each amendment thereto for the purposes of complying with Section 10(a)(3) of the Act (whether by post-effective amendment, incorporated report or form of prospectus), (C) at the Effective Time and (D) on the Closing Date, the Registration Statement conformed and will conform in all material respects to the requirements of the Act and the Rules and Regulations and did not and will not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading and (ii) (A) on its date, (B) at the time of filing the Final Prospectus pursuant to Rule 424(b) and (C) on the Closing Date, the Final Prospectus will conform in all material respects to the requirements of the Act and the Rules and

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Regulations, and will not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein, in light of the circumstances under which they were made, not misleading.  The preceding sentence does not apply to (i) that part of the Registration Statement that constitutes the Statement of Eligibility and Qualification (Form T-1) of the Trustee under the Trust Indenture Act and (ii) statements in or omissions from any such document based upon written information furnished to the Company by any Underwriter through the Representatives specifically for use therein, it being understood and agreed that the only such information is that described as such in Section 8(b) hereof.

(c)  Automatic Shelf Registration Statement.  (i)  Well-Known Seasoned Issuer Status.  (A)  At the time of initial filing of the Registration Statement, (B) at the time of the most recent amendment thereto for the purposes of complying with Section 10(a)(3) of the Act (whether such amendment was by post-effective amendment, incorporated report filed pursuant to Section 13 or 15(d) of the Exchange Act or form of prospectus), and (C) at the time the Company or any person acting on its behalf (within the meaning, for this clause only, of Rule 163(c)) made any offer relating to the Offered Securities in reliance on the exemption of Rule 163, the Company was a “well known seasoned issuer” as defined in Rule 405, including not having been an “ineligible issuer” as defined in Rule 405.

(ii)    Effectiveness of Automatic Shelf Registration Statement.  The Registration Statement is an “automatic shelf registration statement,” as defined in Rule 405, that initially became effective within three years of the date of this Agreement.

(iii)   Eligibility to Use Automatic Shelf Registration Form.  The Company has not received from the Commission any notice pursuant to Rule 401(g)(2) objecting to use of the automatic shelf registration statement form.

(iv)   Filing Fees.  The Company has paid or shall pay the required Commission filing fees relating to the Offered Securities within the time required by Rule 456(b)(1) without regard to the proviso therein and otherwise in accordance with Rules 456(b) and 457(r).

(d)   Ineligible Issuer Status.  (i)  At the earliest time after the filing of the Registration Statement that the Company or another offering participant made a bona fide offer (within the meaning of Rule 164(h)(2)) of the Offered Securities and (ii) at the date of this Agreement, the Company was not and is not an “ineligible issuer,” as defined in Rule 405.

(e)   General Disclosure Package.  As of the Applicable Time, neither (i) the General Use Issuer Free Writing Prospectus(es) issued at or prior to the Applicable Time, the preliminary prospectus supplement, dated September 7, 2010, including the base prospectus, dated June 8, 2009 (which is the most recent Statutory Prospectus distributed to investors generally), any document incorporated by reference therein and the other information, if any, stated in Schedule B to this Agreement to be included in the General Disclosure Package, all considered together (collectively, the “General Disclosure Package”), nor (ii) any individual Limited Use Issuer Free Writing Prospectus, when considered together with the General Disclosure Package, included any untrue statement of a material fact or omitted to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.  The preceding sentence does not apply to statements in or omissions from the General Disclosure Package in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 8(b) hereof.

(f)    Issuer Free Writing Prospectuses.  Each Issuer Free Writing Prospectus, as of its issue date and at all subsequent times through the Closing Date or until any earlier date that the Company notified or notifies the Representatives as described in the next sentence, did not, does not and will not include any information that conflicted, conflicts or will conflict with the information then contained in the Registration Statement.  If at any time following issuance of an Issuer Free Writing Prospectus and prior to the Closing Date there occurred or occurs an event or development as a result of which such Issuer Free Writing Prospectus

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conflicted or would conflict with the information then contained in the Registration Statement or as a result of which such Issuer Free Writing Prospectus, if republished immediately following such event or development, would, when considered together with the rest of the General Disclosure Package, include an untrue statement of a material fact or omitted or would omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading, (i) the Company has promptly notified or will promptly notify Credit Suisse and (ii) the Company has promptly amended or will promptly amend or supplement such Issuer Free Writing Prospectus to eliminate or correct such conflict, untrue statement or omission.

(g)   Good standing of the Company.  The Company has been duly incorporated and is existing and in good standing under the laws of the State of Delaware, with power and authority (corporate and other) to own its properties and conduct its business as described in the General Disclosure Package; and the Company is duly qualified to do business as a foreign corporation in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to so qualify or be in good standing would not, individually or in the aggregate, reasonably be expected to result in a material adverse effect or any development or event involving a prospective material adverse effect on the condition (financial or otherwise), results of operations, business or properties of the Company and its subsidiaries taken as a whole (“Material Adverse Effect”) .

(h)   Significant Subsidiaries.  Each subsidiary of the Company which is a significant subsidiary as defined in Rule 1-02 of Regulation S-X under the Act (a “Significant Subsidiary”) (i) has been duly incorporated and is existing and in good standing under the laws of the jurisdiction of its incorporation and (ii) has the power and authority (corporate and other) to own its properties and conduct its business as described in the General Disclosure Package, except, in the case of clause (ii) above, as would not reasonably be expected to have a Material Adverse Effect; and each Significant Subsidiary of the Company is duly qualified to do business as a foreign corporation in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to so qualify or be in good standing would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect; all of the issued and outstanding capital stock of each Significant Subsidiary of the Company has been duly authorized and validly issued and is fully paid and nonassessable; and except as described in the General Disclosure Package, the capital stock of each Significant Subsidiary owned by the Company, directly or through subsidiaries, is owned free from liens, encumbrances and security interests.

(i)    Execution and Delivery of Indenture.  The Indenture has been duly authorized and has been qualified under the Trust Indenture Act; the Offered Securities have been duly authorized and, when the Offered Securities are delivered and paid for pursuant to this Agreement on the Closing Date, the Indenture will have been duly executed and delivered (assuming the due authorization, execution and delivery of the Indenture by the Trustee), such Offered Securities will have been duly executed, authenticated, issued and delivered (assuming that the Offered Securities have been authenticated in the manner provided for in the Indenture) and will conform in all material respects to the information in the General Disclosure Package and to the description of such Offered Securities contained in the Final Prospectus and the Indenture and such Offered Securities will constitute valid and legally binding obligations of the Company, enforceable in accordance with their terms, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles.

(j)    Absence of Further Requirements.  No consent, approval, authorization or order of, or filing or registration with, any person (including any governmental agency or body or any court) is required for the consummation of the transactions contemplated by this Agreement or the Indenture in connection with the offering, issuance and sale of the Offered Securities by the Company, except such as have been obtained or made and such as may be required under federal or state securities laws and except as disclosed or contemplated in the General Disclosure Package, the Final Prospectus and the Merger Agreement with respect to the Merger.

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(k)   Absence of Defaults and Conflicts Resulting from Transaction.  The issuance and sale by the Company of the Offered Securities and the execution and delivery by the Company of, and the performance by the Company of its obligations under, this Agreement, the Indenture and the Offered Securities will not contravene the certificate of incorporation or by-laws of the Company, any agreement or other instrument filed as a “material contract” with respect to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2009, the Company’s Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2010, the Company’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2010, the Company’s Current Reports on Form 8-K filed with the Commission on July 12, 2010, August 16, 2010 and August 27, 2010, any provision of applicable law or any material judgment, order or decree of any governmental body, agency or court having jurisdiction over the Company or any of its subsidiaries.

(l)    Absence of Existing Defaults and Conflicts.  The Company is not in violation of its organizational documents or in default (or with the giving of notice or lapse of time would be in default) in the performance or observance of any obligation, agreement, covenant or condition contained in any contract, indenture, mortgage, loan agreement, note, lease or other instrument or agreement to which it is a party or by which it or any of its properties may be bound, which violation or default would, individually or in the aggregate, result in a Material Adverse Effect.

(m)  Authorization of Agreement.  This Agreement has been duly authorized, executed and delivered by the Company.

(n)   Possession of Licenses and Permits.  The Company and its subsidiaries possess such certificates, authorities or permits issued by the appropriate state, federal or foreign regulatory agencies or bodies necessary to conduct the business now operated by them as described in the Registration Statement, the General Disclosure Package and the Final Prospects and, to the knowledge of the Company, have not received any notice of proceedings relating to the revocation or modification of any certificates, authorities or permits, except where the failure to possess such certificates, authorities or permits would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect.

(o)   Absence of Labor Dispute.  No labor dispute with the employees of the Company or any of its subsidiaries exists or, to the knowledge of the Company, is imminent that could have a Material Adverse Effect.

(p)   Accurate Disclosure.  The statements in the General Disclosure Package and the Final Prospectus under the headings “Description of the Notes” and “Certain United States Federal Income Tax Consequences” and the description of the Merger contained under the heading “Summary—Aon Corporation—Pending Merger with Hewitt”, insofar as such statements summarize legal matters, agreements, documents or proceedings discussed therein, are accurate and fair summaries of such legal matters, agreements, documents or proceedings and present the information required to be shown.

(q)   Absence of Manipulation.  The Company has not taken, directly or indirectly, any action that is designed to or that has constituted or that would reasonably be expected to cause or result in the stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Offered Securities.

(r)    Internal Controls.  There are no material weaknesses in the Company’s internal controls over financial reporting (“Internal Controls”). Since the date of the latest audited financial statements included in the General Disclosure Package, there has been no change in the Company’s Internal control that has materially affected, or is reasonably likely to materially affect, the Company’s Internal Controls. The Company maintains a system of Internal Controls, including, but not limited to, disclosure controls and procedures, internal controls over accounting matters and financial reporting, an internal audit function and legal and regulatory compliance controls, that comply with Rule 13a-15 under the Exchange Act and are sufficient to provide reasonable assurances that (i) transactions are executed in accordance with management’s general or specific authorizations, (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with U.S. General Accepted Accounting Principles and to

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maintain accountability for assets, (iii) access to assets is permitted only in accordance with management’s general or specific authorization and (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences.

(s)   Litigation.  There are no legal or governmental proceedings pending or, to the knowledge of the Company, threatened to which the Company or any of its subsidiaries is a party or to which any of the properties of the Company or any of its subsidiaries is subject, other than proceedings fairly summarized in all material respects in the General Disclosure Package and proceedings which are not, individually or in the aggregate, reasonably expected to have a Material Adverse Effect on the Company and its subsidiaries or on the power or ability of the Company to perform its obligations under this Agreement, the Indenture or the Offered Securities or to consummate the offering contemplated hereby.

(t)    Financial Statements.  The financial statements included in the Registration Statement, the General Disclosure Package and the Final Prospectus present fairly the financial position of the Company and its consolidated subsidiaries as of the dates shown and their results of operations and cash flows for the periods shown, and such financial statements have been prepared in conformity with the generally accepted accounting principles in the United States applied on a consistent basis. The assumptions used in preparing the pro forma financial statements included in the Registration Statement, the General Disclosure Package and the Final Prospectus provide a reasonable basis for presenting the significant effects directly attributable to the transactions or events described therein, the related pro forma adjustments give appropriate effect to those assumptions, and the pro forma columns therein reflect the proper application of those adjustments to the corresponding historical financial statement amounts. The pro forma financial statements included in each of the most recent Preliminary Prospectus, the Prospectus and the Registration Statement comply as to form in all material respects with the applicable accounting requirements of Regulation S-X under the Securities Act.

(u)   No Material Adverse Change in Business.  Except as disclosed in the General Disclosure Package, since the end of the period covered by the latest audited financial statements included in the General Disclosure Package (i) there has been no change, nor any development or event involving a prospective change, in the condition (financial or otherwise), results of operations, business, properties or prospects of either (A) the Company and its subsidiaries, taken as a whole or (B) the Company and its subsidiaries taken as a whole after giving pro forma effect to the Merger, that is material and adverse, (ii) except as disclosed in or contemplated by the General Disclosure Package, there has been no dividend or distribution of any kind declared, paid or made by the Company on any class of its capital stock or, to the knowledge of the Company on any class of its capital stock, and (iii) except as disclosed in or contemplated by the General Disclosure Package, there has been no material adverse change in the capital stock, short-term indebtedness, long-term indebtedness, net current assets or net assets of the Company and its subsidiaries.

(v)   Merger with Hewitt.  Nothing has come to the Company’s attention that would cause it to believe that the Merger will not be consummated substantially in accordance with the terms described in the General Disclosure Package and the Prospectus.

(w) Authorization of Merger Agreement.  The Merger Agreement has been duly authorized, executed and delivered by the Company and (assuming the due authorization, execution and delivery of the Merger Agreement by the other parties thereto) constitutes a valid and legally binding obligation of the same, enforceable against the Company in accordance with its terms, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles.

(x)    Investment Company Act.  The Company is not and, after giving effect to the offering and sale of the Offered Securities and the application of the proceeds thereof as described in the General Disclosure Package, will not be an “investment company” as defined in the Investment Company Act of 1940, as amended (the “Investment Company Act”).

(y)   No Unlawful Payments. To the knowledge of the Company, (i) except to the extent as could not reasonably be expected to have a Material Adverse Effect and except as disclosed in the General Disclosure

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Package, it is in compliance in all material respects with the United States Foreign Corrupt Practices Act of 1977 (the “Foreign Corrupt Practices Act”) and any other United States and foreign statute or other law, ordinance, rule or regulation concerning corrupting payments (“Corruption Laws”), (ii) except to the extent as could not reasonably be expected to have a Material Adverse Effect, since January 1, 2008 and except as disclosed in the General Disclosure Package, the Company has not been investigated by any government or any arbitrator, tribunal or court of competent jurisdiction, administrative agency or commission or other governmental or quasi-governmental authority or instrumentality (in each case whether Federal, state, local, foreign, international or multinational) (each, a “Governmental Entity”) with respect to, or been given notice by a Governmental Entity of, any violation by the Company of the Foreign Corrupt Practices Act or any other Corruption Laws and (iii) the Company and its subsidiaries have an operational Foreign Corrupt Practices Act/anticorruption compliance program that includes, at a minimum, policies, procedures and training intended to enhance awareness of and compliance by the Company or such subsidiary with the Foreign Corrupt Practices Act and any other applicable Corruption Laws.

(z) Compliance with Money Laundering Laws. The operations of the Company and its subsidiaries are and have been conducted at all times and in all material respects in compliance with applicable financial recordkeeping and reporting requirements of the Currency and Foreign Transactions Reporting Act of 1970, as amended, the money laundering statutes of all jurisdictions to which the Company is subject, the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any governmental agency in any such jurisdiction (collectively, the “Money Laundering Laws”) and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries with respect to the Money Laundering Laws is pending or, to the knowledge of the Company, threatened.

(aa) Compliance with OFAC. None of the Company or any of its subsidiaries or, to the knowledge of the Company, any director, officer, employee or affiliate of the Company or any of its subsidiaries is currently (i) a specially designated national or other blocked person (“SDN”) under the regulations administered by the Office of Foreign Assets Control of the U.S. Department of the Treasury (“OFAC”) or (ii) is organized, located or resident in a country or territory that is the subject of OFAC-administered sanctions, including, without limitation, Burma/Myanmar, Cuba, Iran, North Korea, Sudan and Syria ((i) and (ii) jointly, “Sanctions Targets”); and the Company will not, directly or to the Company’s knowledge, indirectly, use the proceeds of the offering of the Offered Securities, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other person or entity, for the purpose of financing the activities of any person or entity that, at the time of such funding, is a Sanctions Target; it being understood that the reference to “directly” means in the case of the use of the proceeds of the offering of the Offered Securities (i) as consideration for the Merger, payment to the exchange agent for the Merger and (ii) as the special redemption payment in the event of a mandatory redemption of the Notes, payment to The Depository Trust Company.

3.  Purchase, Sale and Delivery of Offered Securities.  On the basis of the representations, warranties and agreements and subject to the terms and conditions set forth herein, the Company agrees to sell to the several Underwriters, and each of the Underwriters agrees, severally and not jointly, to purchase from the Company, at a purchase price of 99.017% of the principal amount of the 2015 Notes, 99.087% of the principal amount of the 2020 Notes and 98.209% of the principal amount of the 2040 Notes plus, in each case, accrued interest from September 7, 2010 to the Closing Date (as hereinafter defined) the respective principal amounts of Offered Securities set forth opposite the names of the Underwriters in Schedule A hereto.

The Company will deliver the Offered Securities to or as instructed by the Representatives for the accounts of the several Underwriters in a form reasonably acceptable to the Representatives against payment of the purchase price by the Underwriters in Federal (same day) funds by wire transfer to an account at a bank acceptable to the Representatives at the office of Davis Polk & Wardwell LLP, 450 Lexington Avenue, New York, NY 10017, at 10:00 A.M., New York time, on September 10, 2010, or at such other time not later than seven full business days thereafter as the Representatives and the Company determine, such time being herein referred to as the “Closing Date”. For purposes of Rule 15c6-1 under the Exchange Act, the Closing Date (if later than the otherwise applicable settlement date) shall be the settlement date for payment of funds and delivery of securities for all the Offered Securities sold pursuant to the offering. The Offered Securities so to be delivered or evidence of their issuance will be made

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available for inspection at the above office of Davis Polk & Wardwell LLP at least 24 hours prior to the Closing Date.

4.  Offering by Underwriters.  It is understood that the several Underwriters propose to offer the Offered Securities for sale to the public as set forth in the Final Prospectus.

5.  Certain Agreements of the Company. The Company agrees with the several Underwriters that:

(a)   Filing of Prospectuses.  The Company has filed or will file each Statutory Prospectus (including the Final Prospectus) pursuant to and in accordance with Rule 424(b)(2) (or, if applicable and consented to by the Representatives, subparagraph (5)) not later than the second business day following the earlier of the date it is first used or the execution and delivery of this Agreement.  The Company has complied and will comply in all material respects with Rule 433.

(b)   Filing of Amendments; Response to Commission Requests.  The Company will promptly advise the Representatives of any proposal to amend or supplement the Registration Statement or any Statutory Prospectus at any time and will offer the Representatives a reasonable opportunity to comment on any such amendment or supplement; and the Company will also advise the Representatives promptly of (i) the filing of any such amendment or supplement, (ii) any request by the Commission or its staff for any amendment to the Registration Statement, for any supplement to any Statutory Prospectus or for any additional information, (iii) the institution by the Commission of any stop order proceedings in respect of the Registration Statement or the threatening of any proceeding for that purpose, and (iv) the receipt by the Company of any notification with respect to the suspension of the qualification of the Offered Securities in any jurisdiction or the institution or threatening of any proceedings for such purpose.  The Company will use its commercially reasonable efforts to prevent the issuance of any such stop order suspending the effectiveness of the Registration Statement or the suspension of any such qualification where such lack of qualification would have a material adverse impact on the offering of Offered Securities contemplated hereby and, if issued, to obtain as soon as possible the withdrawal thereof.

(c)   Continued Compliance with Securities Laws.  If, at any time on or prior to the completion of the public offer and sale of the Offered Securities when a prospectus relating to the Offered Securities is (or but for the exemption in Rule 172 would be) required to be delivered under the Act by any Underwriter or dealer, any event occurs as a result of which the Final Prospectus as then amended or supplemented would include an untrue statement of a material fact or omit to state any material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, or if it is necessary at any time to amend the Registration Statement or supplement the Final Prospectus to comply with the Act, the Company will promptly notify the Representatives of such event and will promptly prepare and file with the Commission and furnish, at its own expense, to the Underwriters and the dealers and any other dealers upon request of the Representatives, an amendment or supplement which will correct such statement or omission or an amendment which will effect such compliance; provided that any such amendment or supplement required to be prepared after 90 days following the Closing Date shall be at the expense of the Underwriters. Neither the Representatives’ consent to, nor the Underwriters’ delivery of, any such amendment or supplement shall constitute a waiver of any of the conditions set forth in Section 7 hereof.

(d)   Rule 158.  As soon as practicable, but not later than 16 months, after the date of this Agreement, the Company will make generally available to its securityholders an earnings statement covering a period of at least 12 months beginning after the date of this Agreement and satisfying the provisions of Section 11(a) of the Act and Rule 158.

(e)   Furnishing of Prospectuses.  The Company will furnish to the Representatives copies of the Registration Statement, including all exhibits, any Statutory Prospectus, the Final Prospectus and all amendments and supplements to such documents, in each case as soon as available and in such quantities as the Representatives reasonably request during such period of time after the first date of the public offering of the Offered Securities as is required by law to be delivered (or required to be delivered but for

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Rule 172 under the Act) by any Underwriter.  The Company will pay the expenses of printing and distributing to the Underwriters all such documents.

(f)    Blue Sky Qualifications.  The Company will arrange for the qualification of the Offered Securities for sale and the determination of their eligibility for investment under the laws of such jurisdictions as the Representatives designate and will continue such qualifications in effect so long as required for the distribution; provided that the Company shall not be required to (i) qualify as a foreign corporation or other entity or as a dealer in securities in any jurisdiction where it would not otherwise be required to so qualify, (ii) file any general consent to service of process in any such jurisdiction or (iii) subject itself to taxation in any such jurisdiction if it is not otherwise so subject.

(g)   Reporting Requirements.  For so long as the Offered Securities remain outstanding, the Company will furnish to the Representatives and, upon request, to each of the other Underwriters, as soon as practicable after the end of each fiscal year, a copy of its annual report to stockholders for such year; and the Company will furnish to the Representatives (i) as soon as available, a copy of each report and any definitive proxy statement of the Company filed with the Commission under the Exchange Act or mailed to stockholders, and (ii) from time to time, such other information concerning the Company as the Representatives may reasonably request.  However, so long as the Company is subject to the reporting requirements of either Section 13 or Section 15(d) of the Exchange Act and is timely filing reports with the Commission on its Electronic Data Gathering, Analysis and Retrieval system (“EDGAR”), it is not required to furnish such reports or statements to the Underwriters.

(h)   Payment of Expenses.  The Company will pay all expenses incident to the performance of its obligations under this Agreement, including but not limited to any filing fees and other expenses incurred in connection with qualification of the Offered Securities for sale under the blue sky laws of such U.S. jurisdictions as the Representatives designate (including fees and disbursements of counsel to the Underwriters associated with such qualification) and the preparation and printing of memoranda relating thereto, any fees charged by investment rating agencies for the rating of the Offered Securities, costs and expenses relating to investor presentations or any “road show” in connection with the offering and sale of the Offered Securities including, without limitation, any travel expenses of the Company’s officers and employees and any other expenses of the Company including the chartering of airplanes, fees and expenses incident to listing the Offered Securities on the New York Stock Exchange, American Stock Exchange, NASDAQ Stock Market and other national and foreign exchanges, fees and expenses in connection with the registration of the Offered Securities under the Exchange Act, and expenses incurred in distributing preliminary prospectuses and the Final Prospectus (including any amendments and supplements thereto) to the Underwriters and for expenses incurred for preparing, printing and distributing any Issuer Free Writing Prospectuses to investors or prospective investors. It is understood, however, that, except as provided in this Agreement, the Underwriters will pay all of their costs and expenses, including fees and expenses of counsel to the Underwriters, transfer taxes payable on resale of the Offered Securities by them and any advertising expenses connected with any offers they make.

(i)    Use of Proceeds.  The Company will use the net proceeds received in connection with this offering in the manner described in the “Use of Proceeds” section of the General Disclosure Package.

(j)    Absence of Manipulation.  The Company will not take, directly or indirectly, any action designed to or that would constitute or that might reasonably be expected to cause or result in, stabilization or manipulation of the price of any securities of the Company to facilitate the sale or resale of the Offered Securities.

(k)   Restriction on Sale of Securities.  The Company will not offer, sell, contract to sell, pledge or otherwise dispose of, directly or indirectly, or file with the Commission a registration statement under the Act relating to United States dollar-denominated debt securities issued or guaranteed by the Company and having a maturity of more than one year from the date of issue, or publicly disclose the intention to make any such offer, sale, pledge, disposition or filing, without the prior written consent of the Representatives for a period beginning on the date hereof and ending on the Closing Date.

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6.  Free Writing Prospectuses.  (a) Issuer Free Writing Prospectuses.  The Company represents and agrees that, unless it obtains the prior consent of the Representatives, and each Underwriter represents and agrees that, unless it obtains the prior consent of the Company and the Representatives, it has not made and will not make any offer relating to the Offered Securities that would constitute an Issuer Free Writing Prospectus, or that would otherwise constitute a “free writing prospectus,” as defined in Rule 405, required to be filed with the Commission.  Any such free writing prospectus consented to by the Company and the Representatives is hereinafter referred to as a “Permitted Free Writing Prospectus.”  The Company represents that it has treated and agrees that it will treat each Permitted Free Writing Prospectus as an “issuer free writing prospectus,” as defined in Rule 433, and has complied and will comply in all material respects with the requirements of Rules 164 and 433 applicable to any Permitted Free Writing Prospectus, including timely Commission filing where required, legending and record keeping.

(b)  Term Sheets.  The Company will prepare a final term sheet relating to the Offered Securities, containing only information that describes the final terms of the Offered Securities and otherwise in a form consented to by the Representatives, and will file such final term sheet within the period required by Rule 433(d)(5)(ii) following the date such final terms have been established for all classes of the offering of the Offered Securities.  Any such final term sheet is an Issuer Free Writing Prospectus and a Permitted Free Writing Prospectus for purposes of this Agreement.  The Company also consents to the use by any Underwriter of a free writing prospectus that contains only (i)(x) information describing the preliminary terms of the Offered Securities or their offering or (y) information that describes the final terms of the Offered Securities or their offering and that is included in the final term sheet of the Company contemplated in the first sentence of this subsection or (ii) other information that is not “issuer information,” as defined in Rule 433, it being understood that any such free writing prospectus referred to in clause (i) or (ii) above shall not be an Issuer Free Writing Prospectus for purposes of this Agreement.

7.  Conditions of the Obligations of the Underwriters. The obligations of the several Underwriters to purchase and pay for the Offered Securities on the Closing Date will be subject to the accuracy of the representations and warranties of the Company herein (as though made on the Closing Date), to the accuracy of the statements of Company officers made pursuant to the provisions hereof, to the performance by the Company of its obligations hereunder and to the following additional conditions precedent:

(a)  Aon Accountants’ Comfort Letter.  The Representatives shall have received letters, dated, respectively, the date hereof and the Closing Date, of Ernst & Young LLP confirming that they are a registered public accounting firm and independent public accountants with respect to the Company within the meaning of the Securities Laws and substantially in the form of Schedule C-1 hereto with respect to the Company (except that, in any letter dated the Closing Date, the specified date referred to in Schedule C-1 hereto shall be a date no more than three days prior to the Closing Date).

(b)  Hewitt Accountants’ Comfort Letter.  The Representatives shall have received letters, dated, respectively, the date hereof and the Closing Date, of Ernst & Young LLP confirming that they are a registered public accounting firm and independent public accountants with respect to Hewitt within the meaning of the Securities Laws and substantially in the form of Schedule C-2 hereto with respect to Hewitt (except that, in any letter dated the Closing Date, the specified date referred to in Schedule C-2 hereto shall be a date no more than three days prior to the Closing Date).

(c)  Filing of Prospectus.  The Final Prospectus shall have been filed with the Commission in accordance with the Rules and Regulations and Section 5(a) hereof. No stop order suspending the effectiveness of the Registration Statement or of any part thereof shall have been issued and no proceedings for that purpose shall have been instituted or, to the knowledge of the Company or any Underwriter, shall be contemplated by the Commission.

(d)  No Material Adverse Change.  Subsequent to the execution and delivery of this Agreement, there shall not have occurred (i) any change, or any development or event involving a prospective change, in the condition (financial or otherwise), results of operations, business or properties of either (A) the Company and its subsidiaries taken as a whole or (B) the Company and its subsidiaries taken as a whole after giving pro forma effect to the Merger which, in the judgment of the Representatives, is material and adverse and

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makes it impractical or inadvisable to market the Offered Securities; (ii) any downgrading in the rating of any debt securities or preferred stock of the Company by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 436(g)), or any public announcement that any such organization has under surveillance or review its rating of any debt securities or preferred stock of the Company (other than an announcement with positive implications of a possible upgrading, and no implication of a possible downgrading, of such rating) or any announcement that the Company has been placed on negative outlook; (iii)  any change in U.S. or international financial, political or economic conditions or currency exchange rates or exchange controls the effect of which is such as to make it, in the judgment of the Representatives, impractical to market or to enforce contracts for the sale of the Offered Securities, whether in the primary market or in respect of dealings in the secondary market; (iv) any suspension or material limitation of trading in securities generally on the New York Stock Exchange, or any setting of minimum or maximum prices for trading on such exchange; (v) any suspension of trading of any securities of the Company on any exchange or in the over-the-counter market; (vi) any banking moratorium declared by any U.S. federal or New York authorities; (vii) any major disruption of settlements of securities, payment, or clearance services in the United States or any other country where such securities are listed or (viii) any attack on, outbreak or escalation of hostilities or act of terrorism involving the United States, any declaration of war by Congress or any other national or international calamity or emergency if, in the judgment of the Representatives, the effect of any such attack, outbreak, escalation, act, declaration, calamity or emergency is such as to make it impractical or inadvisable to market the Offered Securities or to enforce contracts for the sale of the Offered Securities.

(e)  Opinion of the General Counsel of Company.  The Representatives shall have received an opinion, dated the Closing Date, of Peter Lieb, General Counsel of the Company, in form and substance reasonably satisfactory to the Representatives, to the effect set forth in Schedule D hereto.

(f)  Opinion of Counsel for Company.  The Representatives shall have received an opinion, dated the Closing Date, of Sidley Austin LLP, counsel for the Company, in form and substance reasonably satisfactory to the Representatives, to the effect set forth in Schedule E hereto.

(g)  Opinion of Counsel for Underwriters.  The Representatives shall have received from Davis Polk & Wardwell LLP, counsel for the Underwriters, such opinion or opinions, dated the Closing Date, with respect to such matters as the Representatives may reasonably require, and the Company shall have furnished to such counsel such documents as they request for the purpose of enabling them to pass upon such matters.

(h)  Officer’s Certificate.  The Representatives shall have received a certificate, dated the Closing Date, of an executive officer of the Company and a principal financial or accounting officer of the Company in which such officers shall state that: the representations and warranties of the Company in clauses (a), (c), (d), (e), (f), (j), (k), (m), (p), (q), (v), (w), (x) and (aa) of Section 2 of this Agreement are true and correct in all material respects; the representations and warranties of the Company in clauses (b), (g), (h), (i), (l), (n), (o), (r), (s), (t), (u), (y) and (z) of Section 2 of this Agreement are true and correct; the Company has complied in all material respects with all agreements and satisfied all conditions on its part to be performed or satisfied hereunder at or prior to the Closing Date; no stop order suspending the effectiveness of the Registration Statement has been issued and no proceedings for that purpose have been instituted or, to the best of their knowledge and after reasonable investigation, are contemplated by the Commission; and, subsequent to the dates of the most recent financial statements in the General Disclosure Package, there has been no material adverse change, nor any development or event involving a prospective material adverse change, in the condition (financial or otherwise), results of operations, business or properties of the Company and its subsidiaries taken as a whole except as set forth in the General Disclosure Package or as described in such certificate.

The Company will furnish the Representatives with such conformed copies of such opinions, certificates, letters and documents as the Representatives reasonably request.  The Representatives may in their sole discretion waive on behalf of the Underwriters compliance with any conditions to the obligations of the Underwriters hereunder.

8.  Indemnification and Contribution.  (a)  Indemnification of Underwriters.  The Company will indemnify and hold harmless each Underwriter, its partners, members, directors, officers, employees, agents, affiliates and each

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person, if any, who controls such Underwriter within the meaning of Section 15 of the Act or Section 20 of the Exchange Act (each, an “Indemnified Party”), against any and all losses, claims, damages or liabilities, joint or several, to which such Indemnified Party may become subject, under the Act, the Exchange Act, other Federal or state statutory law or regulation or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon any untrue statement or alleged untrue statement of any material fact contained in any part of the Registration Statement at any time, any Statutory Prospectus as of any time, the Final Prospectus or any Issuer Free Writing Prospectus, or arise out of or are based upon the omission or alleged omission of a material fact required to be stated therein or necessary to make the statements therein, in light of the circumstances under which they were made, not misleading, and will reimburse each Indemnified Party for any legal or other expenses reasonably incurred by such Indemnified Party in connection with investigating or defending against any loss, claim, damage, liability, action, litigation, investigation or proceeding whatsoever (whether or not such Indemnified Party is a party thereto), whether threatened or commenced, and in connection with the enforcement of this provision with respect to any of the above as such expenses are incurred; provided, however, that the Company will not be liable in any such case to the extent that any such loss, claim, damage or liability arises out of or is based upon an untrue statement or alleged untrue statement in or omission or alleged omission from (i) that part of the Registration Statement that constitutes the Form T-1 of the Trustee under the Trust Indenture Act and (ii) any of such documents in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in subsection (b) below.

(b)  Indemnification of Company.  Each Underwriter will severally and not jointly indemnify and hold harmless the Company, each of its directors and each of its officers who signs a Registration Statement and each person, if any, who controls the Company within the meaning of Section 15 of the Act or Section 20 of the Exchange Act (each, an “Underwriter Indemnified Party”), against any losses, claims, damages or liabilities to which such Underwriter Indemnified Party may become subject, under the Act, the Exchange Act, other Federal or state statutory law or regulation or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon any untrue statement or alleged untrue statement of any material fact contained in any part of the Registration Statement at any time, any Statutory Prospectus as of any time, the Final Prospectus, or any Issuer Free Writing Prospectus, or arise out of or are based upon the omission or the alleged omission of a material fact required to be stated therein or necessary to make the statements therein not misleading, in each case to the extent, but only to the extent, that such untrue statement or alleged untrue statement or omission or alleged omission was made in reliance upon and in conformity with written information furnished to the Company by such Underwriter through the Representatives specifically for use therein, and will reimburse any legal or other expenses reasonably incurred by such Underwriter Indemnified Party in connection with investigating or defending against any such loss, claim, damage, liability, action, litigation, investigation or proceeding whatsoever (whether or not such Underwriter Indemnified Party is a party thereto), whether threatened or commenced, based upon any such untrue statement or omission, or any such alleged untrue statement or omission as such expenses are incurred, it being understood and agreed that the only such information furnished by any Underwriter consists of the following information in the General Disclosure Package and the Final Prospectus furnished on behalf of each Underwriter: the concession and reallowance figures appearing in the third paragraph under the caption “Underwriting” and the description of stabilizing transactions, over-allotment transactions, syndicate covering transactions and penalty bids appearing in the eighth paragraph under the caption “Underwriting.”

(c)  Actions against Parties; Notification.  Promptly after receipt by an indemnified party under this Section of notice of the commencement of any action, such indemnified party will, if a claim in respect thereof is to be made against the indemnifying party under subsection (a) or (b) above, notify the indemnifying party of the commencement thereof; but the failure to notify the indemnifying party shall not relieve it from any liability that it may have under subsection (a) or (b) above except to the extent that it has been materially prejudiced (through the forfeiture of substantive rights or defenses) by such failure; and provided further that the failure to notify the indemnifying party shall not relieve it from any liability that it may have to an indemnified party otherwise than under subsection (a) or (b) above.  In case any such action is brought against any indemnified party and it notifies the indemnifying party of the commencement thereof, the indemnifying party will be entitled to participate therein and, to the extent that it may wish, jointly with any other indemnifying party similarly notified, to assume the defense thereof, with counsel satisfactory to such indemnified party (who shall not, except with the consent of the indemnified party, be counsel to the indemnifying party in such action), and after notice from the indemnifying party

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to such indemnified party of its election so to assume the defense thereof, the indemnifying party will not be liable to such indemnified party under this Section for any legal or other expenses subsequently incurred by such indemnified party in connection with the defense thereof other than reasonable costs of investigation.  No indemnifying party shall, without the prior written consent of the indemnified party, effect any settlement of any pending or threatened action in respect of which any indemnified party is or could have been a party and indemnity could have been sought hereunder by such indemnified party unless such settlement (i) includes an unconditional release of such indemnified party from all liability on any claims that are the subject matter of such action and (ii) does not include a statement as to, or an admission of, fault, culpability or a failure to act by or on behalf of an indemnified party.

(d)  Contribution.  If the indemnification provided for in this Section is unavailable or insufficient to hold harmless an indemnified party under subsection (a) or (b) above, then each indemnifying party shall contribute to the amount paid or payable by such indemnified party as a result of the losses, claims, damages or liabilities referred to in subsection (a) or (b) above (i) in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriters on the other from the offering of the Offered Securities or (ii) if the allocation provided by clause (i) above is not permitted by applicable law, in such proportion as is appropriate to reflect not only the relative benefits referred to in clause (i) above but also the relative fault of the Company on the one hand and the Underwriters on the other in connection with the statements or omissions which resulted in such losses, claims, damages or liabilities as well as any other relevant equitable considerations. The relative benefits received by the Company on the one hand and the Underwriters on the other shall be deemed to be in the same proportion as the total net proceeds from the offering (before deducting expenses) received by the Company bear to the total underwriting discounts and commissions received by the Underwriters. The relative fault 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 the Underwriters and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such untrue statement or omission. The amount paid by an indemnified party as a result of the losses, claims, damages or liabilities referred to in the first sentence of this subsection (d) shall be deemed to include any legal or other expenses reasonably incurred by such indemnified party in connection with investigating or defending any action or claim which is the subject of this subsection (d). Notwithstanding the provisions of this subsection (d), no Underwriter shall be required to contribute any amount in excess of the amount by which the total price at which the Securities underwritten by it and distributed to the public were offered to the public exceeds the amount of any damages which such Underwriter 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 Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation. The Underwriters’ obligations in this subsection (d) to contribute are several in proportion to their respective underwriting obligations and not joint.  The Company and the Underwriters agree that it would not be just and equitable if contribution pursuant to this Section 8(d) were determined by pro rata allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation which does not take account of the equitable considerations referred to in this Section 8(d).

9.  Default of Underwriters.  If any Underwriter or Underwriters default in their obligations to purchase 2015 Notes, 2020 Notes and/or 2040 Notes hereunder on the Closing Date and the aggregate principal amount of the applicable series of notes that such defaulting Underwriter or Underwriters agreed but failed to purchase does not exceed 10% of the total principal amount of such series of notes that the Underwriters are obligated to purchase on the Closing Date, the Representatives may make arrangements satisfactory to the Company for the purchase of such notes by other persons, including any of the Underwriters, but if no such arrangements are made by the Closing Date, the non-defaulting Underwriters shall be obligated severally, in proportion to their respective commitments hereunder, to purchase the notes that such defaulting Underwriters agreed but failed to purchase on the Closing Date. If any Underwriter or Underwriters so default and the aggregate principal amount of 2015 Notes, 2020 Notes and/or 2040 Notes with respect to which such default or defaults occur exceeds 10% of the total principal amount of such series of notes that the Underwriters are obligated to purchase on the Closing Date and arrangements satisfactory to the Representatives and the Company for the purchase of such notes by other persons are not made within 36 hours after such default, this Agreement will terminate without liability on the part of any non-defaulting Underwriter or the Company, except as provided in Section 10. As used in this Agreement, the term “Underwriter” includes any person substituted for an Underwriter under this Section. Nothing herein will relieve a defaulting Underwriter from liability for its default.

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10. Survival of Certain Representations and Obligations.  The respective indemnities, agreements, representations, warranties and other statements of the Company or its officers and of the several Underwriters set forth in or made pursuant to this Agreement will remain in full force and effect, regardless of any investigation, or statement as to the results thereof, made by or on behalf of any Underwriter, the Company or any of their respective representatives, officers or directors or any controlling person, and will survive delivery of and payment for the Offered Securities. If the purchase of the Offered Securities by the Underwriters is not consummated for any reason other than solely because of the termination of this Agreement pursuant to Sections 7(d)(iii), 7(d)(iv), 7(d)(vi), 7(d)(vii), 7(d)(viii) and 9 hereof, the Company will reimburse the Underwriters for all out-of-pocket expenses (including fees and disbursements of counsel) reasonably incurred by them in connection with the offering of the Offered Securities, and the respective obligations of the Company and the Underwriters pursuant to Section 8 hereof shall remain in effect.  In addition, if any Offered Securities have been purchased hereunder, the representations and warranties in Section 2 and all obligations under Section 5 shall also remain in effect.

11. Notices. All communications hereunder will be in writing and, if sent to the Underwriters, will be mailed, delivered or telegraphed and confirmed to the Representatives, c/o Credit Suisse Securities (USA) LLC, Eleven Madison Avenue, New York, N.Y. 10010-3629, Attention:  LCD-IBD, or, if sent to the Company, will be mailed, delivered or telegraphed and confirmed to it at Aon Corporation, 200 East Randolph Street, Chicago, Illinois 60601, Attention: Executive Vice President and General Counsel; provided, however, that any notice to an Underwriter pursuant to Section 8 will be mailed, delivered or telegraphed and confirmed to such Underwriter.

12.  Successors. This Agreement will inure to the benefit of and be binding upon the parties hereto and their respective successors and the officers and directors and controlling persons referred to in Section 8, and no other person will have any right or obligation hereunder.

13. Representation of Underwriters.  The Representatives will act for the several Underwriters in connection with this financing, and any action under this Agreement taken by the Representatives jointly will be binding upon all the Underwriters.

14.  Counterparts.  This Agreement may be executed in any number of counterparts, each of which shall be deemed to be an original, but all such counterparts shall together constitute one and the same Agreement.

15.  Headings.  The headings herein are included for convenience of reference only and are not intended to be part of, or to affect the meaning or interpretation of this Agreement.

16.  Absence of Fiduciary Relationship.  The Company acknowledges and agrees that:

(a)           No Other Relationship.  The Representatives have been retained solely to act as underwriters in connection with the sale of Offered Securities and that no fiduciary, advisory or agency relationship between the Company and the Representatives has been created in respect of any of the transactions contemplated by this Agreement or the Final Prospectus, irrespective of whether the Representatives have advised or is advising the Company on other matters;

(b)           Arms’ Length Negotiations.  The price of the Offered Securities set forth in this Agreement was established by the Company following discussions and arms-length negotiations with the Representatives and the Company is capable of evaluating and understanding and understands and accepts the terms, risks and conditions of the transactions contemplated by this Agreement;

(c)           Absence of Obligation to Disclose.  The Company has been advised that the Representatives and their affiliates are engaged in a broad range of transactions which may involve interests that differ from those of the Company and that the Representatives have no obligation to disclose such interests and transactions to the Company by virtue of any fiduciary, advisory or agency relationship; and

(d)           Waiver.  The Company waives, to the fullest extent permitted by law, any claims it may have against the Representatives for breach of fiduciary duty or alleged breach of fiduciary duty and agrees that the Representatives shall have no liability (whether direct or indirect) to the Company in respect of such a fiduciary duty

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claim or to any person asserting a fiduciary duty claim on behalf of or in right of the Company, including stockholders, employees or creditors of the Company.

17.  Applicable Law. This Agreement shall be governed by, and construed in accordance with, the laws of the State of New York.

The Company and the Underwriters hereby submit to the non-exclusive jurisdiction of the Federal and state courts in the Borough of Manhattan in The City of New York in any suit or proceeding arising out of or relating to this Agreement or the transactions contemplated hereby.  The Company and the Underwriters irrevocably and unconditionally waive any objection to the laying of venue of any suit or proceeding arising out of or relating to this Agreement or the transactions contemplated hereby in Federal and state courts in the Borough of Manhattan in The City of New York and irrevocably and unconditionally waives and agrees not to plead or claim in any such court that any such suit or proceeding in any such court has been brought in an inconvenient forum.

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If the foregoing is in accordance with the Representatives’ understanding of our agreement, kindly sign and return to the Company one of the counterparts hereof, whereupon it will become a binding agreement between the Company and the several Underwriters in accordance with its terms.

Very truly yours,

The foregoing Underwriting Agreement is hereby confirmed and
accepted as of the date first above written.

SCHEDULE A

SCHEDULE B

1.     General Use Free Writing Prospectus (included in the General Disclosure Package)

“General Use Issuer Free Writing Prospectus” means:

The final term sheet, dated September 7, 2010, a copy of which is attached hereto as Annex I.

2.     Other Information Included in the General Disclosure Package

The following information is also included in the General Disclosure Package:

None

ANNEX I

Final Term Sheet

SCHEDULE C-1

Comfort Letter of Ernst & Young LLP regarding Aon Corporation

SCHEDULE C-2

Comfort Letter of Ernst & Young LLP regarding Hewitt Associates, Inc.

SCHEDULE D

Opinion of the General Counsel of the Company

SCHEDULE E

Opinion of Counsel for the Company