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) April 30, 1999

                               FIRSTAR CORPORATION
                    (Exact Name of Registrant as Specified in Charter)
                                    

Wisconsin                            1-2981                          39-1940778
(State or Other                 (Commission File               (I.R.S. Employer
Jurisdiction of                     Number)                 Identification No.)
Incorporation)

777 East Wisconsin Avenue, Milwaukee, Wisconsin                           53202
(Address of Principal Executive Offices)                              (Zip Code)


Registrant's telephone number, including area code: (414) 765-4321


                                 Not Applicable
         (Former Name or Former Address, if Changed Since Last Report)





Item 5.     Other Events.

            Firstar Corporation ("Firstar") and Mercantile Bancorporation Inc.
("Mercantile") have entered into an Agreement and Plan of Merger dated as of
April 30, 1999 (the "Merger Agreement"), that provides for the merger of
Mercantile with and into Firstar (the "Merger"). Jerry A. Grundhofer, Firstar's
president and chief executive officer, will continue in that position with the
combined company, which will continue under the name of "Firstar Corporation"
after consummation of the Merger. Thomas H. Jacobsen, Mercantile's chairman,
president and chief executive officer, will upon consummation of the Merger
become chairman of the board of Firstar and will co-chair the board's executive
committee with Mr. Grundhofer. The board of directors of the combined company is
expected to be comprised of 14 directors designated by Firstar and four
directors designated by Mercantile. The Merger is expected to qualify as a
"pooling-of-interests" for accounting purposes and as a "reorganization" under
Section 368(a) of the Internal Revenue Code of 1986, as amended.

            At the effective time of the Merger, each share of common stock, par
value $.01 per share, of Mercantile ("Mercantile Common Stock") outstanding
immediately prior thereto will be converted into the right to receive 2.091
shares of common stock, par value $.01 per share, of Firstar ("Firstar Common
Stock"), plus cash in lieu of fractional shares of Firstar Common Stock.

            Consummation of the Merger is subject to a number of conditions,
including (1) the approval of the Merger Agreement and the transactions
contemplated thereby by the shareholders entitled to vote thereon of each of
Firstar and Mercantile, (2) receipt of all requisite governmental and regulatory
approvals (including the approval of the Board of Governors of the Federal
Reserve System) and (3) certain other customary conditions.

            As an inducement and condition to Firstar's entering into the Merger
Agreement, Mercantile, as issuer, and Firstar, as grantee, entered into a Stock
Option Agreement (the "Mercantile Option Agreement") pursuant to which
Mercantile granted to Firstar an option to purchase 31,415,840 shares of
Mercantile Common Stock (approximately 19.9% of those outstanding) at a price of
$51.25 per share, on certain terms and conditions set forth therein. The option
is exercisable only upon the occurrence of certain events, including the
acquisition by any person of beneficial ownership of 20% or more of the
Mercantile Common Stock then outstanding, or an agreement by Mercantile to
engage in, or the recommendation of Mercantile's Board of Directors that
Mercantile's shareholders approve, any of the following types of business
combinations, other than the Merger: (1) a merger or consolidation, or any
similar transaction, involving Mercantile or any significant subsidiary; (2) a
purchase, lease or other acquisition of all or a substantial portion of the
assets or deposits of Mercantile or any significant subsidiary of Mercantile or
(3) a purchase of securities representing more than 20% of the voting power of
Mercantile.

            As an inducement and condition to Mercantile's entering into the
Merger Agreement, Firstar and Mercantile also entered into a stock option
agreement pursuant to which Firstar has granted to Mercantile an option to
purchase up to 65,460,210 shares of Firstar 



Common Stock (approximately 9.9% of those outstanding) at a price of $31.56 per
share on certain terms and conditions set forth therein that are substantially
identical to those of the Mercantile Option Agreement.

            A copy of the press release dated April 30, 1999 regarding the
Merger is attached as Exhibit 99.1 hereto and is incorporated herein by
reference.

            This current report on Form 8-K and the exhibit hereto contain
forward looking statements with respect to the financial condition, results of
operations and business of Firstar and Mercantile and assuming the consummation
of the Merger, a combined Firstar and Mercantile, including statements relating
to: the synergies (including cost savings) and accretion to reported earnings 
expected to be realized from the Merger; business opportunities and strategies
potentially available to the combined company; and the restructuring charges
expected to be incurred in connection with the Merger. These forward looking
statements involve certain risks and uncertainties. Factors that may cause
actual results to differ materially from those contemplated by such forward
looking statements include, among other things, the following possibilities:
expected cost savings from the Merger cannot be fully realized or realized
within the expected time; revenues following the Merger are lower than expected;
competitive pressure among depository institutions increases significantly;
costs or difficulties related to the integration of the businesses of 
Firstar and Mercantile are greater than expected; changes in the interest rate
environment reduce interest margins; general economic conditions, either
nationally or in the states in which the combined company will be doing
business, are less favorable than expected; legislation or regulatory
requirements or changes adversely affect the business in which the combined
company will be engaged; and changes may occur in the securities market. All
dividends on Firstar Common Stock are subject to determination by the Firstar
board of directors in its discretion.

            Such forward-looking statements speak only as of the date on which
such statements were made, and Firstar undertakes no obligation to update any
forward-looking statement to reflect events or circumstances after the date on
which any such statement is made to reflect the occurrence of unanticipated
events.

Item 7.     Financial Statements and Exhibits.

            (c) The following exhibits are filed with this report:

            Exhibit Number                            Description
                 99.1                   Press Release issued April 30, 1999





                                   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.

                                       FIRSTAR CORPORATION

                                       By:/s/ Jennie P. Carlson
                                          Name: Jennie P. Carlson
                                          Title:Senior Vice President,
                                                General Counsel and
                                                Secretary

Dated:      May 4, 1999