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Exhibit 12(a)

Aon Corporation and Consolidated Subsidiaries
Combined With Unconsolidated Subsidiaries
Computation of Ratio of Earnings to Fixed Charges

			Years Ended December 31,
(millions except ratios)			2004		2003		2002		2001			2000
Income from continuing operations before provision for income taxes and minority interest			$	880	$	1,131	$	840	$	367		$	846
Less: Earnings from unconsolidated entities under the equity method of accounting				34		49		19		(139	)		44
Add back fixed charges:
	Interest on indebtedness			136		101		124		127			140
	Interest credited on deposit-type insurance contracts			1		—		29		56			71
	Portion of rents representative of interest factor			73		67		59		57			54
		Income as adjusted	$	1,056	$	1,250	$	1,033	$	746		$	1,067
Fixed charges:
	Interest on indebtedness (1)		$	136	$	101	$	124	$	127		$	140
	Interest credited on deposit-type insurance contracts			1		—		29		56			71
	Portion of rents representative of interest factor			73		67		59		57			54
		Total fixed charges	$	210	$	168	$	212	$	240		$	265
Ratio of earnings to fixed charges				5.0		7.4		4.9		3.1			4.0

(1)

As a result of the adoption of FIN 46 on December 31, 2003, Aon was required to deconsolidate its 8.205% mandatorily redeemable preferred capital securities. This decrease was offset by an increase in notes payable. Beginning in 2004, interest expense ($58 million for the year ended December 31, 2004) on these notes payable was reported as part of interest expense in the consolidated statements of income.

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Exhibit 12(a)

Aon Corporation and Consolidated Subsidiaries Combined With Unconsolidated Subsidiaries Computation of Ratio of Earnings to Fixed Charges