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Exhibit 12(a)

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

			Three Months Ended March 31,
							Years Ended December 31,
(millions except ratios)
			2004		2003		2003		2002		2001			2000		1999
Income from continuing operations before provision for income taxes and minority interest			$	300	$	268	$	1,132	$	840	$	369		$	850	$	625
Less: Earnings from unconsolidated entities under the equity method of accounting				17		7		49		19		(139	)		44		50
Add back fixed charges:
	Interest on indebtedness			34		28		101		124		127			140		105
	Interest credited on deposit-type insurance contracts			—		1		—		29		56			71		77
	Interest on ESOP			—		—		—		—		—			—		1
	Portion of rents representative of interest factor			15		14		67		59		57			54		49
		Income as adjusted	$	332	$	304	$	1,251	$	1,033	$	748		$	1,071	$	807
Fixed charges:
	Interest on indebtedness(1)		$	34	$	28	$	101	$	124	$	127		$	140	$	105
	Interest credited on deposit-type insurance contracts			—		1		—		29		56			71		77
	Interest on ESOP			—		—		—		—		—			—		1
	Portion of rents representative of interest factor			15		14		67		59		57			54		49
		Total fixed charges	$	49	$	43	$	168	$	212	$	240		$	265	$	232
Ratio of earnings to fixed charges				6.8		7.1		7.4		4.9		3.1			4.0		3.5

(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 ($14 million for the three months ended March 31, 2004) on these notes payable is reported as part of interest expense on the condensed consolidated statements of income.

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Exhibit 12(a)