UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported):  December 17, 2010

MARSHALL & ILSLEY CORPORATION

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code:  (414) 765-7801

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Item 8.01.

Other Events.

On December 17, 2010, BMO Financial Group (“BMO”) and Marshall & Ilsley Corporation (“M&I”) announced that they had entered into an Agreement and Plan of Merger (the “Merger Agreement”), providing for, among other things, the acquisition by BMO of all outstanding shares of common stock of M&I in a stock-for-stock transaction.  Under the terms of the Merger Agreement, M&I will merge with a BMO subsidiary (the “Merger”), and existing M&I shareholders will become entitled to receive common shares of Bank of Montreal.  The Merger is subject to customary closing conditions, including regulatory approvals and approval from the shareholders of M&I.  A copy of the news release announcing the Merger Agreement is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

Item 9.01.

Financial Statements and Exhibits.

(d) Exhibits.

Forward-Looking Statements

This Form 8-K contains forward-looking statements within the meaning of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.  Such forward-looking statements include, without limitation, statements regarding expected financial and operating activities and results that are preceded by, followed by, or that include words such as “may,” “expects,” “anticipates,” “estimates” or “believes.”  Such statements are subject to important factors that could cause M&I’s actual results to differ materially from those anticipated by the forward-looking statements.  These factors include, but are not limited to: (i) the possibility that the Merger does not close when expected or at all because required regulatory, shareholder or other approvals and other conditions to closing are not received or satisfied on a timely basis or at all; (ii) the terms of the Merger may need to be modified to satisfy such approvals or conditions; (iii) the anticipated benefits from the Merger are not realized in the time frame anticipated or at all as a result of changes in general economic and market conditions, interest and exchange rates, monetary policy, laws and regulations (including changes to capital requirements) and their enforcement, and the degree of competition in the geographic and business areas in which M&I operates; (iv) the ability to promptly and effectively integrate the businesses of M&I and BMO; (v) reputational risks and the reaction of M&I’s customers to the transaction; (vi) diversion of management time on merger-related issues; and (vii) those factors referenced in Item 1A. Risk Factors in M&I’s Annual Report on Form 10-K for the year ended December 31, 2009 and as may be described from time to time in M&I’s subsequent SEC filings, which factors are incorporated herein by reference.  Readers are cautioned not to place undue reliance on these forward-looking statements, which reflect only M&I’s belief as of the date of this Form 8-K.  Except as required by federal securities law, M&I undertakes no obligation to

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update these forward-looking statements or reflect events or circumstances after the date of this Form 8-K.

Additional information for shareholders

In connection with the Merger, BMO will file with the Securities and Exchange Commission (the “SEC”) a Registration Statement on Form F-4 that will include a Proxy Statement of M&I, and a Prospectus of Bank of Montreal, as well as other relevant documents concerning the proposed transaction.  Shareholders are urged to read the Registration Statement and the Proxy Statement/Prospectus regarding the Merger when it becomes available and any other relevant documents filed with the SEC, as well as any amendments or supplements to those documents, because they will contain important information.  

A free copy of the Proxy Statement/Prospectus, as well as other filings containing information about BMO and M&I, may be obtained at the SEC’s Internet site (http://www.sec.gov).  You will also be able to obtain these documents, free of charge, from BMO at www.BMO.com under the tab “About BMO - Investor Relations” and then under the heading “Frequently Accessed Documents” or from M&I by accessing M&I’s website at www.MICorp.com under the tab “Investor Relations” and then under the heading “SEC Filings.”

BMO and M&I and certain of their directors and executive officers may be deemed to be participants in the solicitation of proxies from the shareholders of M&I in connection with the Merger.  Information about the directors and executive officers of BMO is set forth in the proxy statement for BMO’s 2010 annual meeting of shareholders, as filed with the SEC on Form 6-K on February 26, 2010.  Information about the directors and executive officers of M&I is set forth in the proxy statement for M&I’s 2010 annual meeting of shareholders, as filed with the SEC on a Schedule 14A on March 12, 2010.  Additional information regarding the interests of those participants and other persons who may be deemed participants in the transaction may be obtained by reading the Proxy Statement/Prospectus regarding the Merger when it becomes available.  Free copies of this document may be obtained as described in the preceding paragraph.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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EXHIBIT INDEX

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