Exhibit 5.2

                [Letterhead of Morris, Nichols, Arsht & Tunnell]


                                 March 7, 1997


M&I Capital Trust A
c/o Marshall & Ilsley Corporation
770 North Water Street
Milwaukee, Wisconsin  53202

     Re:  M&I Capital Trust A
          -------------------

Ladies and Gentlemen:

     We have acted as special Delaware counsel to M&I Capital Trust A, a
Delaware statutory business trust (the "Trust"), in connection with certain
matters relating to the creation of the Trust and the proposed issuance of
Exchange Capital Securities to beneficial owners pursuant to and as described in
Registration Statement No. 333-19809 (and the Prospectus forming a part thereof)
on Form S-4 filed with the Securities and Exchange Commission on January 15,
1997, as amended by Pre-Effective Amendment No. 1 thereto (as so amended, the
"Registration Statement"). Capitalized terms used herein and not otherwise
herein defined are used as defined in the Amended and Restated Declaration of
Trust of the Trust dated as of December 9, 1996 (the "Governing Instrument").

     In rendering this opinion, we have examined and relied upon copies of the
following documents in the forms provided to us: the Certificate of Trust of the
Trust as filed in the Office of the Secretary of State of the State of Delaware
(the "State Office") on December 2, 1996 (the "Certificate of Trust"); a
Declaration of Trust of the Trust dated as of December 2, 1996 (the "Original
Governing Instrument"); the Governing Instrument; the Indenture dated as of
December 9, 1996 between Marshall & Ilsley Corporation, a Wisconsin corporation
("M&I"), and The Chase Manhattan Bank, as Trustee, and the form of First
Supplemental Indenture to be entered into in connection therewith; the Guarantee
Agreement to be entered into between M&I and The Chase Manhattan Bank, as
Trustee, relating to the Exchange Capital Securities; the Registration Rights
Agreement dated December 2, 1996 among the Trust, M&I and the "Initial
Purchasers" (as defined therein) (the "Registration Rights Agreement"); the
Registration Statement; and a certificate of good standing of the Trust obtained
as of a recent date from the State Office. In such examinations, we have assumed
the genuineness of all signatures, the conformity to original documents of all
documents submitted to us as drafts or copies or forms of documents to be
executed and the legal capacity of natural persons to complete the execution of
documents. We have further assumed for purposes of this opinion: (i) the due
formation or organization, valid existence and good standing of each entity
(other than the Trust) that is a


M&I Capital Trust A
March 7, 1997
Page 2
 
party to any of the documents reviewed by us under the laws of the jurisdiction
of its respective formation or organization; (ii) the due authorization,
execution and delivery by, or on behalf of, each of the parties thereto of the
above-referenced documents (including, without limitation, the due
authorization, execution and delivery of the Governing Instrument and the
Registration Rights Agreement prior to the first issuance of Exchange Capital
Securities); (iii) that no event has occurred subsequent to the filing of the
Certificate of Trust that would cause a dissolution or liquidation of the Trust
under the Original Governing Instrument or the Governing Instrument, as
applicable; (iv) that the activities of the Trust have been and will be
conducted in accordance with the Original Governing Instrument or the Governing
Instrument, as applicable, and the Delaware Business Trust Act, 12 Del. C. (S)
3801 et seq. (the "Delaware Act"); (v) that each Person that will acquire
Exchange Capital Securities in the "Exchange Offer" (as defined in the
Registration Statement and as used herein, the "Exchange Offer") will validly
tender Initial Capital Securities in exchange therefor, that such Initial
Capital Securities will be duly accepted, and that such Person will duly receive
Exchange Capital Security Certificates in consideration thereof, all in
accordance with the terms and conditions of the Governing Instrument, the
Registration Statement and the Registration Rights Agreement and that the
Exchange Capital Securities are otherwise issued and sold to the Exchange
Capital Securities Holders in accordance with the terms, conditions,
requirements and procedures set forth in the Governing Instrument, the
Registration Statement and the Registration Rights Agreement; and (vi) that the
documents examined by us are in full force and effect, express the entire
understanding of the parties thereto with respect to the subject matter thereof
and have not been modified, supplemented or otherwise amended, except as herein
referenced. We have not reviewed any documents other than those identified above
in connection with this opinion, and we have assumed that there are no other
documents that are contrary to or inconsistent with the opinions expressed
herein. Further, we express no opinion with respect to, and assume no
responsibility for the contents of, the Registration Statement or any other
offering material relating to the Exchange Capital Securities. No opinion is
expressed herein with respect to the requirements of, or compliance with,
federal or state securities or blue sky laws. As to any fact material to our
opinion, other than those assumed, we have relied without independent
investigation on the above-referenced documents and on the accuracy, as of the
date hereof, of the matters therein contained.

     Based on and subject to the foregoing, and limited in all respects to
matters of Delaware law, it is our opinion that:

     1.  The Trust is a duly created and validly existing business trust in good
standing under the laws of the State of Delaware.

     2.  The Exchange Capital Securities, upon issuance pursuant to the Exchange
Offer, will constitute validly issued and, subject to the qualifications set
forth in paragraph 3 below, fully paid and nonassessable beneficial interests in
the assets of the Trust.

 
M&I Capital Trust A
March 7, 1997
Page 3

     3.  Under the Delaware Act and the terms of the Governing Instrument, each
Exchange Capital Security Holder of the Trust, in such capacity, will be
entitled to the same limitation of personal liability extended to stockholders
of private corporations for profit organized under the General Corporation Law
of the State of Delaware; provided, however, we express no opinion with respect
to the liability of any Exchange Capital Security Holder who is, was or may
become a named Trustee of the Trust. Notwithstanding the foregoing, we note that
pursuant to Section 11.4 of the Governing Instrument, the Trust may withhold
amounts otherwise distributable to a Holder and pay over such amounts to the
applicable jurisdictions in accordance with federal, state and local law and any
amount withheld will be deemed to have been distributed to such Holder and that,
pursuant to the Governing Instrument, Exchange Capital Security Holders may be
obligated to make payments or provide indemnity or security under the
circumstances set forth therein.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the use of our name and reference to our opinion
under the heading "LEGAL MATTERS" in the Prospectus forming a part thereof. In
giving this consent, we do not thereby admit that we come within the category of
persons whose consent is required under Section 7 of the Securities Act of 1933,
as amended, or the rules and regulations of the Securities and Exchange
Commission thereunder. This opinion speaks only as of the date hereof and is
based on our understandings and assumptions as to present facts, and on our
review of the above-referenced documents and the application of Delaware law as
the same exist as of the date hereof, and we undertake no obligation to update
or supplement this opinion after the date hereof for the benefit of any person
or entity with respect to any facts or circumstances that may hereafter come to
our attention or any changes in facts or law that may hereafter occur of take
effect. This opinion is intended solely for the benefit of the addressee hereof
in connection with the matters contemplated hereby and may not be relied on by
any other person or entity or for any other purpose without our prior written
consent.

                                 Very truly yours,

                                 MORRIS, NICHOLS, ARSHT & TUNNELL

                                 /s/ Morris, Nichols, Arsht & Tunnell