Exhibit 5

                      G O D F R E Y   &   K A H N,  S. C.
                               ATTORNEYS AT LAW
                            780 NORTH WATER STREET
                           MILWAUKEE, WI 53202-3590
                                 www.gklaw.com

PHONE:   414-273-3500                                        FAX:   414-273-5198



                                 May 30, 2001



Marshall & Ilsley Corporation
770 North Water Street
Milwaukee, Wisconsin  53202

Ladies and Gentlemen:

     Reference is made to the Registration Statement on Form S-4 (the
"Registration Statement") to be filed by Marshall & Ilsley Corporation (the
"Corporation") with the Securities and Exchange Commission (the "Commission")
pursuant to the Securities Act of 1933, as amended (the "Securities Act") with
respect to shares of common stock of the Corporation, $1.00 par value ("Common
Stock") issuable in connection with the merger (the "Merger") of the Corporation
and National City Bancorporation, as described in the Proxy Statement-Prospectus
included in the Registration Statement.

     As counsel to the Corporation, we are familiar with the Restated Articles
of Incorporation and the By-laws of the Corporation.  We have also examined, or
caused to be examined, such other documents and instruments and have made, or
caused to be made, such further investigation as we have deemed necessary or
appropriate to enable us to render this opinion.

     Based upon the foregoing, it is our opinion that the shares of Common Stock
of the Corporation when issued upon the effectiveness of the Merger and
delivered to the holders of common stock of National City Bancorporation will be
validly issued, fully paid and nonassessable, subject to Section 180.0622(2)(b)
of the Wisconsin Statutes.

     Section 180.0622(2)(b) of the Wisconsin Statutes provides that shareholders
of a corporation may be assessed up to the par value of their shares to satisfy
the obligations of such corporation to its employees for services rendered, but
not exceeding six months service in the case of any individual employee.
Certain Wisconsin courts have interpreted "par value" to mean the full amount
paid by the purchaser of shares upon issuance thereof.

     We hereby consent to the use of this opinion as Exhibit 5 to the
Registration Statement and to the reference to our firm under the caption "Legal
Matters" in the prospectus that is a part of the Registration Statement. In
giving such consent, we do not admit that we are in the category of persons
whose consent is required under Section 7 of the Securities Act or the rules and
regulations of the Commission issued thereunder.

                              Very truly yours,

                              /s/  Godfrey & Kahn, S.C.

                              GODFREY & KAHN, S.C.