Exhibit 12(a)

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

	Three Months Ended
	Mar. 31,					Years Ended December 31,
(millions except ratios)	2006			2005		2005		2004		2003		2002		2001
Income from continuing operations before provision for income taxes and minority interest	$	304		$	310	$	965	$	827	$	1,074	$	787	$	306
Less: Earnings from unconsolidated entities under the equity method of accounting	(1		)	1		7		34		49		19		(139		)
Add back fixed charges:
Interest on indebtedness (1)	31			34		125		136		101		124		127
Interest credited on deposit-type insurance contracts	—			—		—		1		—		29		56
Portion of rents representative of interest factor	18			18		71		73		67		59		57
Income as adjusted	$	354		$	361	$	1,154	$	1,003	$	1,193	$	980	$	685
Fixed charges:
Interest on indebtedness(1)	$	31		$	34	$	125	$	136	$	101	$	124	$	127
Interest credited on deposit-type insurance contracts	—			—		—		1		—		29		56
Portion of rents representative of interest factor	18			18		71		73		67		59		57
Total fixed charges	$	49		$	52	$	196	$	210	$	168	$	212	$	240
Ratio of earnings to fixed charges	7.2			6.9		5.9		4.8		7.1		4.6		2.9

(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 both the three months ended March 31, 2006 and 2005 and $58 million for the years ended December 31, 2005 and 2004) on these notes payable is reported as part of interest expense on the condensed consolidated statements of income.