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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)
			2003		2002		2002		2001		2000		1999		1998
Income before provision for income taxes and minority interest			$	256	$	271	$	793	$	309	$	854	$	635	$	931
Add back fixed charges:
	Interest on indebtedness			28		29		124		127		140		105		87
	Interest credited on investment-type insurance contracts			1		12		29		56		71		77		72
	Interest on ESOP			—		—		—		—		—		1		2
	Portion of rents representative of interest factor			14		15		59		57		54		49		51
		Income as adjusted	$	299	$	327	$	1,005	$	549	$	1,119	$	867	$	1,143
Fixed charges:
	Interest on indebtedness		$	28	$	29	$	124	$	127	$	140	$	105	$	87
	Interest credited on investment-type insurance contracts			1		12		29		56		71		77		72
	Interest on ESOP			—		—		—		—		—		1		2
	Portion of rents representative of interest factor			14		15		59		57		54		49		51
		Total fixed charges	$	43	$	56	$	212	$	240	$	265	$	232	$	212
Ratio of earnings to fixed charges				7.0		5.8		4.7		2.3		4.2		3.7		5.4

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Exhibit 12(a)

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