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                                                             Exhibits 5 and 23.3








                               Firstar Corporation
                            777 East Wisconsin Avenue
                           Milwaukee, Wisconsin 53202



                                December 17, 1998


Securities & Exchange Commission
Judiciary Plaza
450 Fifth Street, N.W.
Washington, D.C.  20549

     Re:  Firstar Corporation
          Star Banc Thrift Savings (401(k)) Plan
          --------------------------------------

Dear Sir or Madam:

     I have acted as counsel for Firstar Corporation, a Wisconsin corporation
(the "Corporation"), in connection with its assumption of obligations under the
Star Banc Thrift Savings (401(k)) Plan (the "Plan") as a result of mergers and a
reorganization, completed on November 20, 1998, involving, among others, the
Corporation and Star Banc Corporation. I have examined such documents, records
and matters of law as I deemed necessary for purposes of this opinion and, based
thereupon, am of the opinion that the shares of common stock, $0.01 par value,
of the Corporation which may be issued and sold pursuant to the Plan will be,
when issued and sold in accordance with the terms of the Plan, duly authorized,
validly issued, fully paid and nonassessable.

     I hereby consent to the filing of this opinion as an Exhibit to the
Registration Statement on Form S-8 to be filed by the Corporation with the
Securities and Exchange Commission to effect registration under the Securities
Act of 1933 of the shares to be sold pursuant to the Plan.

                                       Very truly yours,

                                       /s/ Jennie P. Carlson

                                       Jennie P. Carlson
                                       Senior Vice President, General Counsel
                                          and Secretary