8-K

                       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

                         MERCANTILE BANCORPORATION INC.
               (Exact Name of Registrant as Specified in Charter)

Missouri                            1-11792                          43-0951744
(State or Other                 (Commission File               (I.R.S. Employer
Jurisdiction of                     Number)                 Identification No.)
Incorporation)

P.O. Box 524, St. Louis, Missouri                                    63166-0524
(Address of Principal Executive Offices)                             (Zip Code)

Registrant's telephone number, including area code: (314)418-2525

                                 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 hereby incorporated herein by
reference.

            In connection with and prior to entering into the Merger
Agreement and the Mercantile Stock Option Agreement, Mercantile and Harris Trust
and Savings Bank, as Rights Agent ("Harris"), entered into an amendment to the
Rights Agreement, dated as of May 20, 1998, by and between Mercantile and
Harris. A copy of the amendment to the Rights Agreement is attached as Exhibit
4.1 hereto and is hereby incorporated herein by reference.

           This current report on Form 8-K and Exhibit 99.1 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 Mercantile 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
                  4.1                   Amendment, dated as of April 30, 1999,
                                        to Rights Agreement, dated as of May
                                        20, 1998, 



                                        by and between Mercantile
                                        Bancorporation Inc. and Harris Trust
                                        and Savings Bank, as Rights Agent.


                 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.

                                       MERCANTILE BANCORPORATION INC.

                                       By:/s/ John W. McClure 
                                          Name: John W. McClure
                                          Title: Vice Chairman and 
                                                 Chief Financial Officer

Dated:      May 4, 1999

EX-4

                       AMENDMENT NO. 1 TO RIGHTS AGREEMENT

            This AMENDMENT NO. 1, dated as of April 30, 1999 (this "Amendment"),
is between Mercantile Bancorporation Inc., a Missouri corporation (the
"Corporation"), and Harris Trust and Savings Bank, as Rights Agent (the "Rights
Agent").

                                    Recitals

            WHEREAS, the Corporation and the Rights Agent are parties to a
Rights Agreement, dated as of May 20, 1998 (the "Rights Agreement"); and

            WHEREAS, Firstar Corporation, a Wisconsin corporation ("Firstar")
and the Corporation propose to enter into an Agreement and Plan of Merger (the
"Merger Agreement") pursuant to which Mercantile will merge with and into the
Corporation (the "Merger"), and a related Stock Option Agreement by and between
the Corporation, as issuer, and Firstar, as grantee (the "Option Agreement").
The Board of Directors of the Corporation has approved the Merger Agreement, the
Merger and the Option Agreement; and

            WHEREAS, pursuant to Section 27 of the Rights Agreement, the Board
of Directors of the Corporation has determined that an amendment to the Rights
Agreement as set forth herein is necessary and desirable in connection with the
foregoing and the Corporation and the Rights Agent desire to evidence such
amendment in writing;

            NOW, THEREFORE, in consideration of the foregoing and the mutual
agreements set forth herein, the parties hereto agree as follows:

            (a) Amendment of Section 1(a). Section 1(a) of the Rights Agreement
is amended to add the following sentence at the end thereof:

      "Notwithstanding anything in this Rights Agreement to the contrary,
      Firstar shall not be deemed to be an Acquiring Person by virtue of (i) the
      consummation of the Merger, (ii) the execution and delivery of the Merger
      Agreement and the Option Agreement, or (iii) the consummation of any of
      the other transactions contemplated in the Merger Agreement and the Option
      Agreement."

             (b) Amendment of Section 3(a). Section 3(a) of the Rights Agreement
is amended to add the following sentence at the end thereof:

      "Notwithstanding anything in this Rights Agreement to the contrary, a
      Distribution Date shall not be deemed to have occurred as the result of
      (i) the consummation of the Merger, (ii) the execution of the Merger
      Agreement and the Option Agreement or (iii) the consummation of any of the
      other transactions contemplated in the Merger Agreement and the Option
      Agreement."

            (c) Amendment of Section 1(h). Section 1(h) of the Rights Agreement
is amended and restated to read as follows:


                        (i)"Exchange Act" shall mean the Securities and
                           Exchange Act of 1934, as amended.

                        (ii) "Merger" shall have the meaning set forth in the
                           Merger Agreement.

                        (iii) "Merger Agreement" shall mean that certain
                            Agreement and Plan of Merger, dated as of April 30,
                            1999, by and between Firstar and the Corporation, as
                            amended from time to time.

                        (iv)"Option Agreement" shall mean that certain Stock
                            Option Agreement, dated as of April 30, 1999, by and
                            between Firstar, as grantee, and the Corporation, as
                            issuer, as amended from time to time.

                        (v) "Firstar" shall mean Firstar Corporation, a
                            Wisconsin corporation.

            (d) Amendment of Section 7(a). Section 7(a) of the Rights Agreement
is hereby amended and restated to state in its entirety as follows:

            The registered holder of any Right Certificate may exercise the
            Rights evidenced thereby (except as otherwise provided herein) in
            whole or in part at any time after the Distribution Date upon
            surrender of the Right Certificate, with the form of election to
            purchase on the reverse side thereof duly executed, to the Rights
            Agent at the principal office of the Rights Agent together with
            payment of the Purchase Price for each one one-hundredth of a share
            of Preferred Stock as to which the Rights are exercised, at or prior
            to the Close of Business on the earlier of (i) June 3, 2008 (the
            "Final Expiration Date"), (ii) the time at which the Rights are
            redeemed as provided in Section 23 hereof, (iii) the time at which
            the Rights are exchanged as provided in Section 24 hereof or (iv)
            the consummation of the Merger (such earlier date being herein
            referred to as the "Expiration Date").

            (e) Amendment of Section 13. Section 13 of the Rights Agreement is
amended to add the following sentence at the end thereof:

      "Notwithstanding anything in this Rights Agreement to the contrary, none
      of (i) the consummation of the Merger, (ii) the execution of the Merger
      Agreement and the Option Agreement and (iii) the consummation of any of
      the other transactions contemplated in the Merger Agreement and the Option
      Agreement shall be deemed to be events of the type described in the first
      sentence of this Section 13, and shall not cause the Rights to be adjusted
      or exercisable in accordance with, or any other action to be taken or
      obligation to arise pursuant to, this Section 13."

                                      -2-



            (f) Effectiveness. This Amendment shall be deemed effective as of
the date first written above, as if executed on such date. Except as amended
hereby, the Rights Agreement shall remain in full force and effect and shall be
otherwise unaffected hereby.

            (g) Miscellaneous. This Amendment shall be deemed to be a contract
made under the laws of the State of Missouri and for all purposes shall be
governed by and construed in accordance with the laws of such state applicable
to contracts to be made and performed entirely within such state, except as to
the duties and liabilities of the Rights Agent which shall be governed by and
construed in accordance with the laws of the State of Illinois. This Amendment
may be executed in any number of counterparts, each of such counterparts shall
for all purposes be deemed to be an original, and all such counterparts shall
together constitute but one and the same instrument. If any term, provision,
covenant or restriction of this Amendment is held by a court of competent
jurisdiction or other authority to be invalid, void or unenforceable, the
remainder of the terms, provisions, covenants and restrictions of this Amendment
shall remain in full force and effect and shall in no way be affected, impaired
or invalidated. It is the intent of the parties hereto to enforce the remainder
of the terms, provisions, covenants and restrictions to the maximum extent
permitted by law.

                                      -3-



            IN WITNESS WHEREOF, the parties hereto have caused this Amendment
No. 1 to be duly executed, all as of the date and year first above written.

Attest:                                   MERCANTILE BANCORPORATION INC.

By:  /s/ Michael J. Marshall              By:  /s/ Mary K. Granberg
Name: Michael J. Marshall                 Name: Mary K. Granberg
Title:  Assistant Secretary and           Title:  Senior Vice President
Senior Attorney

Attest:                                   HARRIS TRUST AND SAVINGS BANK,
                                          AS RIGHTS AGENT

By:  /s/ Susan M. Shadel                  By:   /s/ Charles V. Zade
Name:  Susan M. Shadel                    Name: Charles V. Zade
Title: Vice President                     Title: Vice President



                                      -4-

EX-99

NEWS RELEASE
                                                FOR IMMEDIATE RELEASE
                                                Contact:
                                                        Steve Dale (Media)
                                                        (414) 765-4455
                                                        Joe Messinger (Analysts)
                                                        (414)765-5235          

                     Firstar Agrees to Acquire Mercantile,
                 Creating $75 Billion Midwest Banking Franchise

 Transaction to Provide 8.5 Percent EPS Accretion in 1999, 10.7 Percent in 2000

MILWAUKEE and ST. LOUIS, April 30, 1999--Firstar Corporation
(NYSE:FSR) today announced that it has signed a definitive agreement to
acquire Mercantile Bancorporation Inc. (NYSE:MTL) through an exchange of
shares valued at approximately $10.6 billion.

Under the terms of the agreement, Mercantile shareholders will receive a
tax-free exchange of 2.091 shares of Firstar common stock for each share of
Mercantile common stock owned. Based on Firstar's closing stock price on April
29, 1999 (the date the exchange rate was finalized) this represents a price of
$66.00 for each Mercantile share, a premium of 29 percent over Mercantile's
closing price of $51.25 per share on that date, and a multiple of 21.6 times
Mercantile's 1999 estimated earnings per share.

This transaction will create the second largest Midwest banking franchise,
providing a full line of consumer banking, commercial banking and trust and
investment management services and products to more than 5 million customers
through its approximately 1,180 branch locations in nine Midwest states and
Tennessee, Arkansas and Arizona, plus trust operations in Florida. The combined
company would become the 13th largest bank holding company in the United States,
with assets of more than $75 billion, deposits of $59 billion, assets under
management of $67 billion and a market capitalization of $32 billion.

After the closing, the combined company expects to pay dividends at an annual
rate of $0.65 per common share. This approximates a continuation of the current
$1.36 dividend rate paid on Mercantile shares, adjusted for the exchange ratio.
This dividend rate would represent an increase of 63 percent on the current
$0.40 annual dividend rate paid on Firstar shares. The combined companies'
corporate headquarters will remain in Milwaukee, with St. Louis becoming the
headquarters for corporate banking and Cincinnati continuing as the headquarters
for consumer banking.

Jerry A. Grundhofer, Firstar's president and chief executive officer, will
continue in that position. Thomas H. Jacobsen, Mercantile's chairman, president
and chief executive officer, who will be based in St. Louis, will become
chairman of the board of Firstar and will co-chair the board's executive
committee with Grundhofer. Roger L. Fitzsimonds, Firstar's current chairman,
plans to retire upon the closing of the acquisition and will be 



named chairman emeritus at that time. The board of directors will be comprised 
of 14 representatives of Firstar and four representatives of Mercantile.

"We are announcing today the combination of two excellent banks with long and
distinguished histories, outstanding people, and superior potential for future
growth," said Grundhofer. "Together, we will create a preeminent Midwest
franchise in financial services. By combining our franchises we will continue to
build critical mass in our key business lines, with emphasis on sales, customer
service and strong industry-leading technology. We will be a rapidly growing,
very profitable, highly efficient organization with a continued strong
commitment to community involvement. This merger will provide enhanced benefits
for our customers, our employees and our communities, as well as, unmatched
economic benefits for shareholders of both companies."

"Combining with Firstar is a uniquely attractive strategic opportunity for
Mercantile," said Jacobsen, "not only for the economic benefits it offers our
shareholders, but also for the continuity of quality customer service and
community involvement for St. Louis, Kansas City and our entire banking
franchise. Firstar has proven that it can combine a highly effective operating
style with strong local market involvement. We are delighted to be combining
with a bank whose priorities are so completely compatible with our own. Each of
us has products, skills and resources to bring to the other. We look forward to
a seamless integration of our two companies into a single regional banking
leader."

The transaction will be accounted for as a pooling of interests, and is expected
to close in the fourth quarter of 1999. It is expected to be 8.5 percent
accretive to Firstar's earnings per share in 1999, and 10.7 percent accretive in
2000. This accretion is based on anticipated expense reductions, and does not
include earnings from revenue enhancements or the reinvestment of excess
capital. Firstar expects to incur pre-tax merger-related and restructuring
charges of $428 million between the closing of the transaction and the end of
2000.

Firstar and Mercantile estimate that they will reduce their expenses by $169
million, with 100 percent of these savings to be achieved in 2000. These cost
savings represent 19 percent of Mercantile's current expense base, and would
bring the combined company into line with Firstar's current efficiency ratio.
The cost saving opportunities include centralization of corporate activities,
consolidation of data processing and operations, optimization of commercial
banking, retail branches and alternative delivery channels for bank products and
services, improvements in technology, and reconfiguration of mortgage, credit
card and asset management businesses. Systems conversion will begin after year
end and continue throughout the year 2000.

Additionally, the companies believe there is significant opportunity for future
revenue growth resulting from product cross-selling, accelerated consumer loan
growth, new product introductions, and increased scale in key business lines,
including consumer, commercial and small business lending, asset management,
mortgage banking, correspondent banking and cash management. Customers of the
combined company will have access to approximately 1180 branches, the nation's
seventh-largest system and more than 2000 ATM's, the tenth-largest system and a
broad range of electronic banking, 



PC banking and Internet banking products and services. The combined company will
rank in the top five in share of deposits in Missouri, Iowa, Wisconsin, 
Kentucky, Minnesota, Arkansas, Ohio, Illinois, and Kansas, and also have a 
presence in Indiana, Tennessee, Arizona and Florida.

Firstar's highly successful incentive-based compensation program, known as "Pay
for Performance" will be implemented throughout the combined company. This
program provides all employees with incentive pay linked to individual
performance and selected measures of shareholder value creation. Also, Firstar
is the only bank in the country to guarantee its quality customer service with
its unique "Five Star Service Guarantee" in all lines of business.

"It is essential today that when companies combine, they do so seamlessly," said
Jacobsen. "We are heartened by the speed and smoothness of the recent Star
Banc-Firstar merger; combined with our own experience in post-transaction
integration, it leads us to believe that together we can minimize near-term
disruptions as we create our region's premier banking institution. The
compatibility of our cultures will facilitate the process, and the scale and
growth of the resulting organization will create new opportunities for all our
people."

"The strongest banks grow from deep local roots. Firstar has consciously
nurtured its links to its core markets, and we intend to bring this same sense
of nurture to the deep ties that Mercantile has developed over many decades in
St. Louis, and other important markets in Missouri, Arkansas, Kansas, Iowa,
Illinois and Kentucky," said Grundhofer. "It is important to note that
throughout Firstar, today and in the future, all our business lines will have a
strong local presence, with local decision-making authority. We will continue to
maintain key processing and mortgage production centers in St. Louis. In
addition to our business activities and our local market involvement, we will
continue Mercantile's impressive community commitments. I will be spending the
majority of my time in St. Louis for the foreseeable future, and Tom and I look
forward to meeting with leaders of the community to discuss how we can best
preserve and enhance the citizenship role Mercantile has long played in the
community."

The transaction, which was approved by the boards of both companies, is subject
to normal shareholder and regulatory approvals. Both companies have completed
due diligence, including Year 2000 compliance issues. In connection with the
merger agreement, Firstar and Mercantile have each granted the other
cross-options to purchase common shares of the other company under certain
circumstances.

Firstar was advised in this transaction by the investment bank of Credit
Suisse/First Boston. The investment bank of Donaldson, Lufkin & Jenrette
provided a fairness opinion and acted as financial advisor to Mercantile. Morgan
Stanley Dean Witter also rendered a fairness opinion to Mercantile.

Firstar Corporation is a $38 billion bank holding company with approximately 720
full-service banking offices in Ohio, Wisconsin, Kentucky, Illinois, Indiana,
Iowa, Minnesota, Tennessee and Arizona. Firstar offers a full complement of
banking, trust,



investment, insurance, securities brokerage and other financial services. 
Firstar Corporation is the parent company of Firstar Finance, a consumer finance
company and Firstar Investment Research & Management Company, LLC (FIRMCO), an 
investment advisory firm. Visit Firstar on the web at www.Firstar.com. Firstar 
was founded in 1853.

Mercantile is a $36 billion multi-bank holding company headquartered in St.
Louis, which operates banks in nearly 500 locations in Missouri, Iowa, Kansas,
Illinois, Arkansas and Kentucky. Mercantile's non-banking subsidiaries include
companies providing brokerage services, asset-based lending, factoring, 
investment advisory services, leasing services and credit life and other 
insurance products as agent.

                                      ###

This news release contains 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 cost savings and revenue
enhancements and accretion to reported earnings that will be realized from the
merger; 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 of the difficulties
related to the integration of the business 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.