Exhibit 12

Marshall & Ilsley Corporation

Computation of Ratio of Earnings to Fixed Charges

($000’s)

	Years Ended December 31,
	2003			2002			2001			2000			1999
Earnings:
Earnings before income taxes, extraordinary items and cumulative effect of changes in accounting principles	$	758,387		$	718,592		$	501,045		$	470,350		$	527,939
Fixed charges, excluding interest on deposits		267,379			301,518			321,059			321,812			222,172
Earnings including fixed charges but excluding interest on deposits		1,025,766			1,020,110			822,104			792,162			750,111
Interest on deposits		228,216			283,385			566,899			772,016			585,864
Earnings including fixed charges and interest on deposits	$	1,253,982		$	1,303,495		$	1,389,003		$	1,564,178		$	1,335,975
Fixed Charges:
Interest Expense:
Short-term borrowings	$	81,070		$	150,310		$	188,587		$	224,187		$	142,294
Long-term borrowings		163,348			127,343			110,842			78,773			63,145
One-third of rental expense for all operating leases (the amount deemed representative of the interest factor)		22,961			23,865			21,630			18,852			16,733
Fixed charges excluding interest on deposits		267,379			301,518			321,059			321,812			222,172
Interest on deposits		228,216			283,385			566,899			772,016			585,864
Fixed charges including interest on deposits	$	495,595		$	584,903		$	887,958		$	1,093,828		$	808,036
Ratio of Earnings to Fixed Charges:
Excluding interest on deposits		3.84	x		3.38	x		2.56	x		2.46	x		3.38	x
Including interest on deposits		2.53	x		2.23	x		1.56	x		1.43	x		1.65	x