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                    [WHYTE HIRSCHBOECK DUDEK S.C. LETTERHEAD]

            

                                                                     EXHIBIT 5.1



                                 April 27, 1999

Board of Directors
Anchor BanCorp Wisconsin Inc.
25 West Main Street
Madison, WI  53703

         Re:      Merger of Anchor BanCorp Wisconsin Inc.
                  and FCB Financial Corp.
                  Form S-4 Registration Statement


Gentlemen and Ms. Cremer Berkenstadt:

         We have acted as counsel to Anchor BanCorp Wisconsin Inc., a Wisconsin
corporation (the "Registrant"), in connection with the preparation and filing of
a Registration Statement on Form S-4, including the Joint Proxy
Statement/Prospectus included as a part thereof (the "Registration Statement"),
to be filed with the Securities and Exchange Commission under the Securities Act
of 1933, as amended (the "Securities Act"), relating to the Registrant's
proposed issuance of up to 7,449,974 shares of the Registrant's $0.10 par value
common stock, including an equal number of preferred share purchase rights
associated therewith (the "Stock"), in connection the Registrant's proposed
merger (the "Merger") with FCB Financial Corp. ("FCB") as contemplated by the
Agreement and Plan of Merger dated January 5, 1999 (the "Merger Agreement") by
and between the Registrant and FCB.

         We have examined Registration Statement, including the Joint Proxy
Statement/ Prospectus included as a part thereof, and the originals, or
photostatic, certified or conformed copies of such records of Registrant,
certificates of its officers and such other documents as we have deemed relevant
and necessary, as a basis for the opinion set forth herein, including without
limitation, the Registrant's current Articles of Incorporation and Bylaws. In
connection with such examinations, we have assumed the authenticity of all
documents 


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WHYTE                                              Anchor BanCorp Wisconsin Inc.
HIRSCHBOECK                                                       April 27, 1999
DUDEK S.C.                                                                Page 2


submitted to us as originals or duplicate originals, the conformity to original
documents of all documents submitted to us as certified, photostatic or
conformed copies, the authenticity of the originals of such latter documents,
and the correctness and completeness of such certificates on which we have
relied.

         Based on the foregoing, it is our opinion that, subject to applicable
regulatory and shareholder approvals of the Merger and the Merger Agreement and
any transactions contemplated thereby, the securities being offered by the
Registrant, when issued as contemplated by the Registration Statement, will be
legally issued, fully paid and nonassessable, subject to the limitation
contained in Section 180.0622(2)(b), Wisconsin Statutes, which makes
shareholders personally liable for debts owing to employees for services
performed for the Registrant not exceeding six months service, up to the par
value of the shares they own. We note that "par value" has been construed by a
Wisconsin court for this purpose to mean the initial purchase price of the
stock.

         We hereby consent to the filing of this opinion as an exhibit to the
above-referenced Registration Statement and any amendments thereto (including
post-effective amendments) and to the reference to this firm and to this opinion
under the caption "LEGAL MATTERS" in the Joint Proxy Statement/Prospectus which
forms a part of the Registration Statement. In giving our consent, we do not
admit that we are "experts" within the meaning of Section 11 of the Securities
Act or within the category of persons whose consent is required by Section 7 of
the Securities Act.

                                   Very truly yours,
                                   WHYTE HIRSCHBOECK DUDEK S.C.

                                   /s/ Andrew J. Guzikowski
                              By:
                                 --------------------------------  
                                   Andrew J. Guzikowski