Exhibit 12

MARSHALL & ILSLEY CORPORATION

Computation of Ratio of Earnings to Fixed Charges

($000’s)

	Years Ended December 31,
	2005			2004			2003			2002			2001
Earnings:
Earnings before income taxes, extraordinary items and cumulative effect of changes in accounting principles	$	1,090,367		$	944,966		$	758,387		$	718,592		$	501,045
Fixed charges, excluding interest on deposits		463,209			281,244			267,379			301,518			321,059
Earnings including fixed charges but excluding interest on deposits		1,553,576			1,226,210			1,025,766			1,020,110			822,104
Interest on deposits		544,920			276,102			228,216			283,385			566,899
Earnings including fixed charges and interest on deposits	$	2,098,496		$	1,502,312		$	1,253,982		$	1,303,495		$	1,389,003
Fixed Charges:
Interest Expense:
Short-term borrowings	$	106,333		$	61,256		$	81,070		$	150,310		$	188,587
Long-term borrowings		330,144			196,440			163,348			127,343			110,842
One-third of rental expense for all operating leases (the amount deemed representative of the interest factor)		26,732			23,548			22,961			23,865			21,630
Fixed charges excluding interest on deposits		463,209			281,244			267,379			301,518			321,059
Interest on deposits		544,920			276,102			228,216			283,385			566,899
Fixed charges including interest on deposits	$	1,008,129		$	557,346		$	495,595		$	584,903		$	887,958
Ratio of Earnings to Fixed Charges:
Excluding interest on deposits		3.35	x		4.36	x		3.84	x		3.38	x		2.56	x
Including interest on deposits		2.08	x		2.70	x		2.53	x		2.23	x		1.56	x