EX-23 23 a2182853zex-23.htm EX-23
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Exhibit 23

CONSENT OF ERNST & YOUNG LLP,
INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Board of Directors and Stockholders
Aon Corporation

        We consent to the incorporation by reference in the Registration Statements of Aon Corporation described in the following table of our reports dated February 27, 2008, with respect to the consolidated financial statements and schedule of Aon Corporation, and the effectiveness of internal control over financial reporting of Aon Corporation, included in this Annual Report (Form 10-K) for the year ended December 31, 2007.

        We consent to the incorporation by reference in the following Registration Statements:

Registration Statement
    
Form
   Number
   Purpose
S-8   33-27984   Pertaining to Aon's savings plan
S-8   33-42575   Pertaining to Aon's stock award plan and stock option plan
S-8   33-59037   Pertaining to Aon's stock award plan and stock option plan
S-3   333-50607   Pertaining to the registration of 369,000 shares of common stock
S-8   333-55773   Pertaining to Aon's stock award plan, stock option plan, and employee stock purchase plan
S-3   333-78723   Pertaining to the registration of debt securities, preferred stock and common stock
S-4   333-57706   Pertaining to the registration of up to 3,852,184 shares of common stock
S-3   333-74364   Pertaining to the registration of debt securities, preferred stock, common stock, share purchase contracts, and share purchase units
S-3   333-100466   Pertaining to the registration as amended of 2,707,018 shares of common stock
S-8   333-103344   Pertaining to the registration of common stock
S-8   333-106584   Pertaining to Aon's deferred compensation plan
S-3   333-134918   Pertaining to the registration of debt securities, preferred stock, common stock, convertible securities, share purchase contracts, share purchase units and guarantees
S-8   333-145928   Pertaining to the registration of common stock
S-8   333-145930   Pertaining to the registration of common stock underlying equity securities issued to Aon's president and chief executive officer

/s/ ERNST & YOUNG LLP

Chicago, Illinois
February 27, 2008



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