Exhibit (12)

MARSHALL & ILSLEY CORPORATION

Computation of Ratio of Earnings to Fixed Charges

($000s)



|                                                                                                               |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|-------------------------------------------------------------------------------------------------------------- |  | ------------------------ | --------- | ---- | - | --------- |  | ---- | --------- | ---- | - | --------- |  | - | ---------
|                                                                                                               |  | Years Ended December 31,
|                                                                                                               |  | 2006                     |           | 2005 |   | 2004      |  | 2003 |           | 2002
|Earnings:                                                                                                      |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|Earnings before income taxes, extraordinary items and cumulative effect of changes in accounting principles    |  | $                        | 1,195,632 |      | $ | 1,057,654 |  | $    | 911,840   |      | $ | 724,507   |  | $ | 683,364  
|Fixed charges, excluding interest on deposits                                                                  |  |                          | 692,646   |      |   | 463,209   |  |      | 281,244   |      |   | 267,379   |  |   | 301,518  
|                                                                                                               |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|Earnings including fixed charges but excluding interest on deposits                                            |  |                          | 1,888,278 |      |   | 1,520,863 |  |      | 1,193,084 |      |   | 991,886   |  |   | 984,882  
|Interest on deposits                                                                                           |  |                          | 1,058,713 |      |   | 544,920   |  |      | 276,102   |      |   | 228,216   |  |   | 283,385  
|                                                                                                               |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|Earnings including fixed charges and interest on deposits                                                      |  | $                        | 2,946,991 |      | $ | 2,065,783 |  | $    | 1,469,186 |      | $ | 1,220,102 |  | $ | 1,268,267
|                                                                                                               |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|Fixed Charges:                                                                                                 |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|Interest Expense:                                                                                              |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|Short-term borrowings                                                                                          |  | $                        | 186,863   |      | $ | 106,333   |  | $    | 61,256    |      | $ | 81,070    |  | $ | 150,310  
|Long-term borrowings                                                                                           |  |                          | 476,625   |      |   | 330,144   |  |      | 196,440   |      |   | 163,348   |  |   | 127,343  
|One-third of rental expense for all operating leases (the amount deemed representative of the interest factor) |  |                          | 29,158    |      |   | 26,732    |  |      | 23,548    |      |   | 22,961    |  |   | 23,865   
|                                                                                                               |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|Fixed charges excluding interest on deposits                                                                   |  |                          | 692,646   |      |   | 463,209   |  |      | 281,244   |      |   | 267,379   |  |   | 301,518  
|Interest on deposits                                                                                           |  |                          | 1,058,713 |      |   | 544,920   |  |      | 276,102   |      |   | 228,216   |  |   | 283,385  
|                                                                                                               |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|Fixed charges including interest on deposits                                                                   |  | $                        | 1,751,359 |      | $ | 1,008,129 |  | $    | 557,346   |      | $ | 495,595   |  | $ | 584,903  
|                                                                                                               |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|Ratio of Earnings to Fixed Charges:                                                                            |  |                          |           |      |   |           |  |      |           |      |   |           |  |   |          
|                                                                                                               |  |                          |           |      |  
|Excluding interest on deposits                                                                                 |  |                          | 2.73 x    |      |   | 3.28 x    |  |      | 4.24 x    |      |   | 3.71 x    |  |   | 3.27 x   
|                                                                                                               |  |                          |           |      |  
|Including interest on deposits                                                                                 |  |                          | 1.68 x    |      |   | 2.05 x    |  |      | 2.64 x    |      |   | 2.46 x    |  |   | 2.17 x