EXHIBIT 12

MARSHALL & ILSLEY CORPORATION

Computation of Ratio of Earnings to Fixed Charges

($000’s)

	Years Ended December 31,
	2004			2003			2002			2001			2000
Earnings:
Earnings before income taxes, extraordinary items and cumulative effect of changes in accounting principles	$	944,966		$	758,387		$	718,592		$	501,045		$	470,350
Fixed charges, excluding interest on deposits		281,244			267,379			301,518			321,059			321,812
Earnings including fixed charges but excluding interest on deposits		1,226,210			1,025,766			1,020,110			822,104			792,162
Interest on deposits		276,102			228,216			283,385			566,899			772,016
Earnings including fixed charges and interest on deposits	$	1,502,312		$	1,253,982		$	1,303,495		$	1,389,003		$	1,564,178
Fixed Charges:
Interest Expense:
Short-term borrowings	$	61,256		$	81,070		$	150,310		$	188,587		$	224,187
Long-term borrowings		196,440			163,348			127,343			110,842			78,773
One-third of rental expense for all operating leases (the amount deemed representative of the interest factor)		23,548			22,961			23,865			21,630			18,852
Fixed charges excluding interest on deposits		281,244			267,379			301,518			321,059			321,812
Interest on deposits		276,102			228,216			283,385			566,899			772,016
Fixed charges including interest on deposits	$	557,346		$	495,595		$	584,903		$	887,958		$	1,093,828
Ratio of Earnings to Fixed Charges:
Excluding interest on deposits		4.36	x		3.84	x		3.38	x		2.56	x		2.46	x
Including interest on deposits		2.70	x		2.53	x		2.23	x		1.56	x		1.43	x