<PAGE>
 
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                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549
 
                               ----------------
 
                                   FORM 10-K
 
                               ----------------
 
                    ANNUAL REPORT PURSUANT TO SECTION 13 OF
                      THE SECURITIES EXCHANGE ACT OF 1934
 
For the fiscal year ended December 31,       Commission File No. 1-11792
                 1998
 
                               ----------------
 
                        Mercantile Bancorporation Inc.
            (Exact name of Registrant as specified in its charter)
 
               Missouri                              43-0951744
       (State of Incorporation)                     (IRS Employer
                                                 Identification No.)
 
             P.O. Box 524                            63166-0524
          St. Louis, Missouri                        (Zip code)
    (Address of principal executive
               offices)
 
       Registrant's telephone number, including area code: 314-418-2525
 
Securities registered pursuant to Section  Name of exchange on which registered:
             12(b) of the Act:       

    (1) Common Stock ($0.01 Par Value)       (1) New York Stock Exchange
    (2) Preferred Stock Purchase Rights      (2) New York Stock Exchange
         
 
       Securities registered pursuant to Section 12(g) of the Act: None
 
   Indicate by check mark whether the Registrant (1) has filed all reports
required to be filed by Section 13 of the Securities Exchange Act of 1934
during the preceding 12 months, and (2) has been subject to such filing
requirements for the past 90 days.  Yes X  No
                                       ---   ---
 
   Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to
the best of Registrant's knowledge, in definitive proxy or information
statements incorporated by reference in Part III of this Form 10-K. [X]
 
   State the aggregate market value of the voting stock held by non-affiliates
of the Registrant as of February 26, 1999: Common Stock, $0.01 par value,
$6,099,118,381
 
   Indicate the number of shares outstanding of each of the Registrant's
classes of common stock, as of February 26, 1999: Common Stock $0.01 par
value, 157,625,883 shares outstanding
 
                      DOCUMENTS INCORPORATED BY REFERENCE
   As provided herein, portions of the documents below are incorporated by
reference:
 
<TABLE>
<CAPTION>
                           Document                             Part--Form 10-K
                           --------                             ---------------
<S>                                                             <C>
Annual Report of the Registrant to its Shareholders for the
 Year Ended December 31, 1998.................................. Parts I, II, IV
Registrant's Proxy Statement for the 1999 Annual Meeting of
 Shareholders.................................................. Part III
</TABLE>
 
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<PAGE>
 
                                    PART I
 
Item 1. Business
 
                                  THE COMPANY
 
   Mercantile Bancorporation Inc. ("Mercantile" or "Corporation") is a bank
holding company which, as of February 26, 1999, owned, directly or indirectly,
all of the stock of Mercantile Bank National Association ("Mercantile Bank"),
six other commercial banks, one trust company, and other non-banking
subsidiaries located in Missouri, Illinois, Iowa, eastern Kansas, northern and
central Arkansas, and western Kentucky. At December 31, 1998, Mercantile
reported consolidated assets of $35,800,177,000, consolidated loans of
$22,311,258,000, consolidated deposits of $25,461,397,000 and consolidated
shareholders' equity of $3,073,755,000. At December 31, 1998, Mercantile Bank
and its consolidated subsidiaries reported assets of $22,653,777,000, loans of
$13,070,938,000, deposits of $15,023,894,000, and shareholder's equity of
$1,762,076,000.
 
   Mercantile has its principal offices at One Mercantile Center, St. Louis,
Missouri 63101 (telephone number 314-418-2525).
 
                                   BUSINESS
 
General
 
   Mercantile was organized on March 10, 1970, as a Missouri corporation for
the purpose of becoming a multi-bank holding company. Mercantile commenced
operations as a bank holding company in March 1971. Since then Mercantile has
acquired and organized additional financial institutions and bank holding
companies located throughout Missouri, Illinois, Iowa, eastern Kansas,
northern and central Arkansas, and western Kentucky.
 
Financial Summary of Mercantile
 
   A financial summary of Mercantile and its consolidated subsidiaries is
detailed below:
 
<TABLE>
<CAPTION>
                                                 December 31
                         -----------------------------------------------------------
                            1998        1997        1996        1995        1994
                         ----------- ----------- ----------- ----------- -----------
                                                 (Thousands)
<S>                      <C>         <C>         <C>         <C>         <C>
Total assets............ $35,800,177 $33,332,190 $24,995,735 $23,651,434 $22,089,195
 
Loans and leases........  22,311,258  21,361,955  16,937,254  15,584,285  14,558,820
Investments in debt and
 equity securities......   9,470,937   8,464,881   5,429,759   5,626,084   5,573,913
Deposits................  25,461,397  24,809,455  19,784,845  18,463,655  17,341,514
Shareholders' equity....   3,073,755   2,762,302   2,263,243   2,210,845   1,897,387
</TABLE>
 
Subsidiaries
 
   The table setting forth the names and locations of Mercantile's subsidiary
financial institutions is included as Exhibit 21 hereto.
 
Services and Transactions with Subsidiaries
 
   Mercantile provides its subsidiaries with advice and specialized services
in the areas of accounting and taxation, budgeting and strategic planning,
employee benefits and human resources, insurance, operations, marketing,
credit analysis and administration, loan support and participations,
investments, auditing, trust, data processing, bank security and banking and
corporate law. A fee is charged by Mercantile for these services. The
responsibility for the management of each subsidiary remains with its Board of
Directors and with the officers elected by each Board. Intercompany
transactions between Mercantile and its subsidiaries are subject to
restrictions of existing laws and accepted principles of fair dealing.
Mercantile uses the premises of Mercantile Bank for its offices and pays
Mercantile Bank a fee for services and facilities furnished to it.
 
                                       1
<PAGE>
 
Employees
 
   At December 31, 1998, Mercantile had 306 full-time equivalent employees,
while Mercantile and its subsidiaries had a combined total of 10,475 full-time
equivalent employees. Mercantile provides a variety of employment benefits and
believes it enjoys a good relationship with its employees.
 
Operations
 
   Financial Services. Through its subsidiaries, Mercantile offers complete
banking and trust services to the consumer, institutional, commercial,
corporate, affluent and agricultural segments of the market areas which it
serves. Services include commercial, real estate, installment and credit card
loans, checking, savings and time deposits, trust and other fiduciary
services, and various other customer services such as brokerage services,
direct equipment lease financing, international banking and safe deposit
services.
 
   Most of Mercantile's subsidiary financial institutions serve only the
general area in which they are located, predominantly in the 7th, 8th and 10th
Federal Reserve Districts. Membership in Mercantile's subsidiary group
provides each subsidiary institution with a means of satisfying the credit
needs of its customers beyond its own legal lending limit.
 
   Trust and Investment Advisory Services. Mercantile, through its
subsidiaries, offers clients all types of fiduciary services, ranging from the
management of funds for individuals, corporate retirement plans and charitable
foundations to the administration of estates and trusts. To investors it
offers portfolio management, advisory and custodian services. Mercantile Trust
Company National Association ("Mercantile Trust") is a federally-chartered
bank which provides personal trust services. Mississippi Valley Advisors Inc.,
a registered investment advisor, among other things, provides investment
advisory services for employee benefit funds, including pension and profit-
sharing plans, endowment funds and registered mutual funds. At December 31,
1998, Mercantile subsidiaries managed investments with a market value of
approximately $25.9 billion and administered $16.2 billion additional in non-
managed assets.
 
   Investment Services. Mercantile Bank offers a wide range of investment
services to individuals, corporations, correspondent banks and others.
Included in those services are foreign exchange, derivative products, money
market and bond trading operations which serve banks and corporations in the
purchase and sale of various investments and/or hedging instruments. In
addition, Mercantile Bank is registered as a municipal securities dealer.
 
   Brokerage Services. Mercantile Investment Services, Inc. ("MISI"), a
subsidiary of Mercantile Bank, is a registered broker/dealer and a member of
both the National Association of Securities Dealers, Inc. ("NASD") and the
Securities Investors Protection Corporation ("SIPC"). MISI currently offers
both retail and discount brokerage services, including execution of
transactions involving stocks, bonds, options, mutual funds and other
securities.
 
   International. Mercantile Bank maintains accounts at 92 foreign banks, and
31 foreign banks maintain accounts at Mercantile Bank. In addition, Mercantile
Bank is engaged in providing its customers with international banking
services. Mercantile Bank and Mercantile Bank--Kansas/Kansas City offer a wide
range of services to their customers involved in international business
including currency exchange and letters of credit. Mercantile Bank maintains a
Hong Kong subsidiary, Mercantile Trade Services Ltd., which enables the bank
to issue, amend and negotiate letters of credit in Hong Kong on behalf of the
bank's importing customers. Customers of other subsidiary banks with a need
for international services are referred to these banks.
 
   Mercantile Bank also maintains a branch in the City of Georgetown in the
Grand Cayman Islands. This branch enables Mercantile Bank to participate in
the Eurodollar market for deposits and loans. At December 31, 1998, total
deposits of the foreign branch amounted to $554,547,000.
 
   Correspondent Banking. In addition to Mercantile's services for individuals
and corporations, its largest subsidiary bank, Mercantile Bank National
Association (St. Louis), is a correspondent bank for approximately 250
commercial banks located primarily in the lower Midwest. Correspondent banking
services to banks in
 
                                       2
<PAGE>
 
Kansas and the Kansas City metropolitan area are provided through Mercantile
Bank--Kansas/Kansas City. Correspondent banking services include the
processing of checks and collection items, financing for acquisitions and
capital augmentation, and assistance with training and operations.
 
Competition
 
   Mercantile's subsidiary financial institutions are subject to intense
competition from other banks and financial institutions in their service
areas, predominantly the 7th, 8th and 10th Federal Reserve Districts. In
making loans, substantial competition is encountered from banks and other
lending institutions such as savings and loan associations, insurance
companies, finance companies, credit unions, factors, small loan companies and
pension trusts. In addition, Mercantile subsidiaries compete for retail
deposits with savings and loan associations, credit unions, insurance
companies and money market mutual funds. The competition provided by other
financial institutions is not limited to those institutions with offices
located in the area served by the particular subsidiary.
 
   Many other institutions also offer some or all of the trust and fiduciary
services performed by Mercantile's subsidiaries. Mercantile Bank competes with
all local institutions and, in the field of corporate pension trust services,
competition is nationwide.
 
Supervision and Regulation
 
   General. As a bank holding company, Mercantile is subject to regulation
under the Bank Holding Company Act of 1956, as amended ("BHCA"), and its
examination and reporting requirements. Under the BHCA, a bank holding company
may not directly or indirectly acquire the ownership or control of more than
5% of the voting shares or substantially all of the assets of any company,
including a bank or savings and loan association, without the prior approval
of the Board of Governors of the Federal Reserve System (the "Federal Reserve
Board"). In addition, bank holding companies are generally prohibited under
the BHCA from engaging in nonbanking activities, subject to certain
exceptions.
 
   Mercantile and its subsidiaries are subject to supervision and examination
by applicable federal and state banking agencies. The earnings of Mercantile's
subsidiaries, and therefore the earnings of Mercantile, are affected by
general economic conditions, management policies and the legislative and
governmental actions of various regulatory authorities, including the Federal
Reserve Board, the Federal Deposit Insurance Corporation ("FDIC"), the Office
of the Comptroller of the Currency (the "Comptroller") and various state
financial institution regulatory agencies. In addition, there are numerous
governmental requirements and regulations that affect the activities of
Mercantile and its subsidiaries.
 
   Certain Transactions with Affiliates. There are various legal restrictions
on the extent to which a bank holding company and certain of its nonbank
subsidiaries can borrow or otherwise obtain credit from its bank subsidiaries.
In general, these restrictions require that any such extensions of credit must
be on non-preferential terms and secured by designated amounts of specified
collateral and be limited, as to the holding company or any one of such
nonbank subsidiaries, to 10% of the lending institution's capital stock and
surplus, and as to the holding company and all such nonbank subsidiaries in
the aggregate, to 20% of such capital stock and surplus.
 
   Payment of Dividends. Mercantile is a legal entity separate and distinct
from its financial institutions and other subsidiaries. The principal source
of Mercantile's revenues is dividends from its financial institution
subsidiaries. Various federal and state statutory provisions limit the amount
of dividends an affiliate financial institution can pay to Mercantile without
regulatory approval. Generally, approval of federal and state bank regulatory
agencies, as appropriate, is required for any dividend if the total of all
dividends declared in any calendar year would exceed the total of the
institution's net profits, as defined by regulatory agencies, for such year
combined with its retained net profits for the preceding two years. In
addition, a national bank or a state member bank may not pay a dividend in an
amount greater than its net profits then on hand. The payment of dividends by
any financial institution subsidiary also may be affected by other factors,
such as the maintenance of adequate capital.
 
                                       3
<PAGE>
 
   Capital Adequacy. The Federal Reserve Board has issued standards for
measuring capital adequacy for bank holding companies. These standards are
designed to provide risk-responsive capital guidelines and to incorporate a
consistent framework for use by financial institutions operating in major
international financial markets. The banking regulators have issued standards
for banks that are similar to, but not identical with, the standards for bank
holding companies.
 
   In general, the risk-related standards require financial institutions and
financial institution holding companies to maintain certain capital levels
based on "risk-adjusted" assets, so that categories of assets with potentially
higher credit risk will require more capital backing than categories with
lower credit risk. In addition, banks and bank holding companies are required
to maintain capital to support off-balance-sheet activities such as loan
commitments. Mercantile and each of its subsidiary financial institutions
exceed all applicable capital adequacy standards.
 
   Support of Subsidiary Banks. Under Federal Reserve Board policy, Mercantile
is expected to act as a source of financial strength to each subsidiary bank
and to commit resources to support each of the subsidiaries in circumstances
where it might not choose to do so absent such a policy. This may be required
at times when Mercantile may not find itself able to provide such support. In
addition, any capital loans by Mercantile to any of its subsidiaries also
would be subordinate in right of payment to deposits and certain other
indebtedness of such subsidiary.
 
   Consistent with this policy regarding bank holding companies serving as a
source of financial strength for their subsidiary banks, the Federal Reserve
Board has stated that, as a matter of prudent banking, a bank holding company
generally should not maintain a rate of cash dividends unless its net income
available to common shareholders has been sufficient to fully fund the
dividends, and the prospective rate of earnings retention appears consistent
with the bank holding company's capital needs, asset quality and overall
financial condition.
 
   FIRREA and FDICIA. The Financial Institutions Reform, Recovery and
Enforcement Act of 1989 ("FIRREA") contains a cross-guarantee provision that
could result in insured depository institutions owned by Mercantile being
assessed for losses incurred by the FDIC in connection with assistance
provided to, or the failure of, any other insured depository institution owned
by Mercantile. Under FIRREA, failure to meet the capital guidelines could
subject a banking institution to a variety of enforcement remedies available
to federal regulatory authorities, including the termination of deposit
insurance by the FDIC.
 
   The Federal Deposit Insurance Corporation Improvement Act of 1991
("FDICIA") made extensive changes to the federal banking laws. FDICIA
instituted certain changes to the supervisory process, including provisions
that mandate certain regulatory agency actions against undercapitalized
institutions within specified time limits. FDICIA contains various other
provisions that may affect the operations of banks and savings institutions.
 
   The prompt corrective action provision of FDICIA requires the federal
banking regulators to assign each insured institution to one of five capital
categories ("well capitalized," "adequately capitalized" or one of three
"undercapitalized" categories) and to take progressively more restrictive
actions based on the capital categorization, as specified below. Under FDICIA,
capital requirements include a leverage limit, a risk-based capital
requirement and any other measure of capital deemed appropriate by the federal
banking regulators for measuring the capital adequacy of an insured depository
institution. All institutions, regardless of their capital levels, are
restricted from making any capital distribution or paying any management fees
that would cause the institution to fail to satisfy the minimum levels for any
relevant capital measure.
 
   The FDIC, the OCC and the Federal Reserve Board adopted capital-related
regulations under FDICIA. Under those regulations, a bank will be well
capitalized if it: (i) had a total risk-based capital ratio of 10% or greater;
(ii) had a ratio of Tier I capital to risk-weighted assets of 6% or greater;
(iii) had a ratio of Tier I capital to adjusted total assets of 5% or greater;
and (iv) was not subject to an order, written agreement, capital directive or
prompt corrective action directive to meet and maintain a specific capital
level for any capital measure. An association will be adequately capitalized
if it was not "well capitalized" and: (i) had a total risk-based capital
 
                                       4
<PAGE>
 
ratio of 8% or greater; (ii) had a ratio of Tier I capital to risk-weighted
assets of 4% or greater; and (iii) had a ratio of Tier I capital to adjusted
total assets of 4% or greater (except that certain associations rated
"Composite 1" under the federal banking agencies' CAMEL rating system in their
most recent examination may be adequately capitalized if their ratios of Tier
I capital to adjusted total assets were 3% or greater). All Mercantile
subsidiary financial institutions as of December 31, 1998 were categorized as
"well capitalized."
 
   Banking agencies also have adopted regulations that mandate that regulators
take into consideration concentrations of credit risk and risks from non-
traditional activities, as well as an institution's ability to manage those
risks, when determining the adequacy of an institution's capital. This
evaluation is made as part of the institution's regular safety and soundness
examination. Banking agencies also have adopted regulations requiring
regulators to consider interest rate risk (when the interest rate sensitivity
of an institution's assets does not match the sensitivity of its liabilities
or its off-balance-sheet position) in the evaluation of a bank's capital
adequacy and have established an explicit risk-based capital charge for
interest rate risk.
 
   Depositor Preference Statute. Legislation enacted in August 1993 provides a
preference for deposits and certain claims for administrative expenses and
employee compensation against an insured depository institution in the
liquidation or other resolution of such an institution by any receiver. Such
obligations would be afforded priority over other general unsecured claims
against such an institution, including federal funds and letters of credit, as
well as any obligation to shareholders of such an institution in their
capacity as such.
 
   FDIC Insurance Assessments. The subsidiary depository institutions of
Mercantile are subject to FDIC deposit insurance assessments. The FDIC has
adopted a risk-based premium schedule. Each financial institution is assigned
to one of three capital groups--well capitalized, adequately capitalized or
undercapitalized--and further assigned to one of three subgroups within a
capital group, on the basis of supervisory evaluations by the institution's
primary federal and, if applicable, state supervisors, and on the basis of
other information relevant to the institution's financial condition and the
risk posed to the applicable insurance fund. The actual assessment rate
applicable to a particular institution will, therefore, depend in part upon
the risk assessment classification so assigned to the institution by the FDIC.
See "--FIRREA and FDICIA."
 
   Interstate Banking and Other Recent Legislation. The Riegle-Neal Interstate
Banking and Branching Efficiency Act of 1994 ("Riegle-Neal"), enacted in 1994,
facilitates the interstate expansion and consolidation of banking
organizations by permitting (i) bank holding companies that are adequately
capitalized and managed to acquire banks located in states outside their home
states regardless of whether such acquisitions are authorized under the law of
the host state, (ii) interstate merger of banks, except for banks located in
Montana and Texas, which states enacted legislation to "opt out" of this
authority, (iii) banks to establish new branches on an interstate basis
provided that such action is specifically authorized by the law of the host
state, (iv) foreign banks to establish, with approval of the regulators in the
United States, branches outside their home states to the same extent that
national or state banks located in the home state would be authorized to do
so, and (v) banks to receive deposits, renew time deposits, close loans,
service loans and receive payments on loans and other obligations as agent for
any bank or thrift affiliate, whether the affiliate is located in the same
state or a different state. One effect of Riegle-Neal is to permit Mercantile
to acquire banks located in any state and to permit bank holding companies
located in any state to acquire banks and bank holding companies in Missouri.
 
   There also have been a number of recent legislative and regulatory
proposals designed to improve the overall financial stability of the United
States banking system, and to provide for other changes in the bank regulatory
structure, including proposals to reduce regulatory burdens on banking
organizations and to expand the nature of products and services banks and bank
holding companies may offer. It is not possible to predict whether or in what
form these proposals may be adopted in the future, and, if adopted, what their
effect will be on Mercantile.
 
                                       5
<PAGE>
 
Statistical Disclosures
 
   The following statistical disclosures, except as noted, are included in the
Annual Report of the Registrant to its Shareholders for the year ended December
31, 1998, and incorporated herein by reference.
 
<TABLE>
<CAPTION>
                                                              Annual Report
Schedule                                                        Reference
--------                                                   -------------------
<S>                                                        <C>
  I. Distribution of Assets, Liabilities and Shareholders'
     Equity; Interest Rates and Interest Differential

     A.  Average Balance Sheets                                        Page 82

     B.  Analysis of Net Interest Earnings (included herein at
         page 7)                                                           N/A

     C.  Taxable-Equivalent Rate-Volume Analysis (included
         herein at page 7)                                                 N/A

 II. Investment Portfolio

     A.  Book Value by Type of Security                        Note F, Page 64

     B.  Maturity Distribution (included herein at page 8)                 N/A

III. Loan Portfolio

     A.  Types of Loans                                    Exhibit 13, Page 39

     B.  Maturities and Sensitivities to Changes in
         Interest Rates                                    Exhibit 13, Page 39

     C.  Risk Elements

         1. Non-Accrual, Past Due and Restructured Loans   Exhibit 16, Page 43
                                                           Exhibit 17, Page 43
                                                               Note A, Page 59

         2. Potential Problem Loans                        Commentary, Page 44

         3. Foreign Outstandings                                             *

 IV. Summary of Loan Loss Experience

     A.  Reserve for Possible Loan Losses                  Exhibit 14, Page 40
                                                           Commentary, Page 40
                                                               Note A, Page 59

     B.  Allocation of the Reserve for Possible Loan       Exhibit 15, Page 41
         Losses

  V. Deposits

     A.  Average Balances and Rates Paid by Deposit Category           Page 82

     B.  Maturity Distribution of Certain CDs and Time
         Deposits                                           Exhibit 7, Page 33

 VI. Return on Equity and Assets                            Exhibit 4, Page 28

VII. Short-term Borrowings (included herein at page 9)                     N/A
</TABLE> 
 
  *There were no significant interest bearing deposits with foreign banks at
  December 31, 1998, 1997 or 1996.
 
                                       6
<PAGE>
 
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TAXABLE-EQUIVALENT RATE-VOLUME ANALYSIS
(Dollars in Millions)
 
<TABLE>
<CAPTION>
                             Average
    Average Volume          Rate(/1/)                                                        Interest
------------------------ ------------------                                            --------------------
 1998     1997    1996   1998  1997   1996                                              1998   1997   1996
-------  ------- ------- ----  -----  -----                                            ------ ------ ------
<S>      <C>     <C>     <C>   <C>    <C>    <C>                                       <C>    <C>    <C>
                                             Interest Income
                                             Loans and leases(/3/)                    
$ 5,539  $ 4,824 $ 4,365 8.20%  8.59%  8.57%   Commercial                              $  454 $  415 $  374
  3,711    3,490   3,208 8.50   8.66   8.66    Real estate--commercial                    315    302    278
    769      661     593 8.66   8.87   9.10    Real estate--construction                   67     59     54
  8,386    6,777   4,340 7.57   7.84   8.10    Real estate--residential mortgage          635    532    352
    552      510     417 9.48   9.69   9.67    Real estate--home equity credit loans       52     49     40
  2,694    2,404   2,217 9.06   9.12   9.18    Consumer                                   244    219    203
    129      636     850 6.63  12.83  12.87    Credit card                                  9     82    110
-------  ------- -------                                                               ------ ------ ------
 21,780   19,302  15,990 8.16   8.59   8.82      Total Loans and Leases                 1,776  1,658  1,411
                                             Investments in debt and equity securities
    135      105      57 6.56   6.80   6.49    Trading                                      9      7      4
  8,630    6,334   5,189 6.47   6.42   6.08    Taxable                                    559    407    315
    425      470     511 8.13   8.13   8.01    Tax-exempt                                  35     38     41
-------  ------- -------                                                               ------ ------ ------
  9,190    6,909   5,757 6.55   6.54   6.25      Total                                    603    452    360
                                             Short-term investments                   
    232      189      71 5.72   5.50   5.83    Due from banks--interest bearing            13     10      4
                                               Federal funds sold and repurchase      
    311      265     267 5.44   6.41   5.67     agreements                                 17     17     15
-------  ------- -------                                                               ------ ------ ------
    543      454     338 5.56   6.03   5.71      Total Short-term Investments              30     27     19
-------  ------- -------                                                               ------ ------ ------
$31,513  $26,665 $22,085 7.64   8.01   8.10      Total Interest Income(/1/)            $2,409 $2,137 $1,790
=======  ======= =======                                                               ====== ====== ======
                                             Interest Expense                         
                                             Interest Bearing Deposits                
$ 3,088  $ 2,935 $ 2,683 1.84   2.01   2.27    Interest bearing demand                 $   57 $   59 $   61
  3,991    3,463   3,029 4.04   4.02   3.64    Money market accounts                      161    139    110
  1,739    1,471   1,351 2.58   2.39   2.34    Savings                                     45     35     32
                                               Consumer time certificates               
  9,574    8,644   7,055 5.54   5.55   5.58     under $100,000                            530    479    393
    185      205     192 5.31   4.62   4.22    Other time                                  10     10      8
-------  ------- -------                                                               ------ ------ ------
 18,577   16,718  14,310 4.32   4.32   4.22      Total Interest Bearing Core Deposits     803    722    604
  1,893    1,675   1,440 5.58   5.64   5.35    Time certificates $100,000 and over        106     95     77
    411      458     184 5.65   5.72   5.70    Foreign                                     23     26     11
-------  ------- -------                                                               ------ ------ ------
  2,304    2,133   1,624 5.59   5.66   5.39      Total Purchased Deposits                 129    121     88
-------  ------- -------                                                               ------ ------ ------
 20,881   18,851  15,934 4.46   4.47   4.34      Total Interest Bearing Deposits          932    843    692
  3,294    2,930   1,671 5.29   5.43   5.37  Short-term borrowings                        174    159     90
     56      175     261 6.09   6.02   5.88  Bank notes                                     4     11     15
  3,050      869     343 5.85   6.72   7.29  Long-term debt(/4/)                          178     58     25
-------  ------- -------                                                               ------ ------ ------
$27,281  $22,825 $18,209 4.72   4.69   4.52      Total Interest Expense                $1,288 $1,071 $  822
=======  ======= =======                                                               ====== ====== ======
                         2.92   3.32   3.58  Net Interest Rate Spread                 
                                             Net Interest Rate Margin                 
                         3.56   4.00   4.38   and Net Interest Income(/1/)             $1,121 $1,066 $  968
                                                                                       ====== ====== ======

                                              <CAPTION>                                    
                                                           Increase (Decrease)              
                                              ---------------------------------------------
                                                    1997 to 1998          1996 to 1997     
                                              ---------------------- ----------------------
                                              Rate(/2/) Vol.  Total  Rate(/2/) Vol.  Total 
                                              --------- ----- ------ --------- ----- ------
                                              <C>       <C>   <C>    <C>       <C>   <C>   
Interest Income                                                                                                                     
Loans and leases(/3/)                                                                                                             
  Commercial                                    $(21)   $ 60  $ 39      $ 1    $ 40  $ 41
  Real estate--commercial                         (6)     19    13       --      24    24
  Real estate--construction                       (2)     10     8       (1)      6     5
  Real estate--residential mortgage              (23)    126   103      (17)    197   180
  Real estate--home equity credit loans           (1)      4     3       --       9     9
  Consumer                                        (1)     26    25       (1)     17    16
  Credit card                                     (8)    (65)  (73)      --     (28)  (28)
                                                ------- ----- ------ --------- ----- ------
    Total Loans and Leases                       (62)    180   118      (18)    265   247
Investments in debt and equity securities                                                
  Trading                                         --       2     2       --       3     3
  Taxable                                          4     148   152       22      70    92
  Tax-exempt                                      --      (3)   (3)       1      (4)   (3)
                                                ------- ----- ------ --------- ----- ------
    Total                                          4     147   151       23      69    92
Short-term investments                                                                   
  Due from banks--interest bearing                 1       2     3       (1)      7     6
  Federal funds sold and repurchase                                                        
   agreements                                     (3)      3    --        2      --     2
                                                ------- ----- ------ --------- ----- ------
    Total Short-term Investments                  (2)      5     3        1       7     8
                                                ------- ----- ------ --------- ----- ------
    Total Interest Income(/1/)                  $(60)   $332  $272      $ 6    $341  $347
                                                ======= ===== ====== ========= ===== ======
Interest Expense                                                                         
Interest Bearing Deposits                                                                
  Interest bearing demand                       $ (5)   $  3  $ (2)     $(8)   $  6  $ (2)
  Money market accounts                            1      21    22       13      16    29
  Savings                                          3       7    10       --       3     3
  Consumer time certificates                                                               
   under $100,000                                 (1)     52    51       (3)     89    86
  Other time                                       1      (1)   --        1       1     2
                                                ------- ----- ------ --------- ----- ------
    Total Interest Bearing Core Deposits          (1)     82    81        3     115   118
  Time certificates $100,000 and over             (1)     12    11        5      13    18
  Foreign                                         --      (3)   (3)      --      15    15
                                                ------- ----- ------ --------- ----- ------
    Total Purchased Deposits                      (1)      9     8        5      28    33
                                                ------- ----- ------ --------- ----- ------
    Total Interest Bearing Deposits               (2)     91    89        8     143   151
Short-term borrowings                             (5)     20    15        2      67    69
Bank notes                                        --      (7)   (7)       1      (5)   (4)
Long-term debt(/4/)                              (27)    147   120       (5)     38    33
                                                ------- ----- ------ --------- ----- ------
    Total Interest Expense                      $(34)   $251  $217      $ 6    $243  $249
                                                ======= ===== ====== ========= ===== ====== 
Net Interest Rate Spread
Net Interest Rate Margin                 
 and Net Interest Income(/1/)
</TABLE>

(/1/)Taxable-equivalent basis includes tax-equivalent adjustments of
    $16,664,000, $18,084,000 and $18,593,000 for 1998, 1997 and 1996,
    respectively, based on a Federal income tax rate of 35%.
(/2/)The rate-volume variance is allocated entirely to rate.
(/3/)Income from loans on non-accrual status is included on a cash basis, while
    non-accrual loan balances are included in average volume.
(/4/)Includes company-obligated mandatorily redeemable preferred securities of
    Mercantile Capital Trust I.
-------------------------------------------------------------------------------
 
                                       7
<PAGE>
 
-------------------------------------------------------------------------------
 
INVESTMENTS IN DEBT AND EQUITY SECURITIES(/1/)
(Dollars in Thousands)
 
<TABLE>
<CAPTION>
                                         December 31, 1998
                  -------------------------------------------------------------------
                         Available-for-sale                   Held-to-maturity
                  --------------------------------     ------------------------------
                                                                 Estimated
                  Amortized  Estimated                 Amortized   Fair
                     Cost    Fair Value Yield(/2/)       Cost      Value   Yield(/2/)
                  ---------- ---------- ----------     --------- --------- ----------
<S>               <C>        <C>        <C>            <C>       <C>       <C>
U.S. Treasury
 Within one year  $  217,801 $  218,971      6.53%      $ 6,513   $ 6,560       6.87%
 One to five
  years               59,619     60,655      6.01            --        --         --
 Five to 10
  years                   --         --        --            --        --         --
 After 10 years           --         --        --            --        --         --
                  ---------- ----------                 -------   -------
  Total              277,420    279,626      6.41         6,513     6,560       6.87
 Average
  Maturity                                      9 mos.                             5 mos.
U.S. Government
 Agencies(/3/)
 Within one year     469,387    471,286      6.36        24,886    24,980       6.25
 One to five
  years            4,105,446  4,137,876      6.27        64,355    65,984       8.32
 Five to 10
  years            1,400,245  1,408,487      6.21            --        --         --
 After 10 years       19,318     19,746      6.71            --        --         --
                  ---------- ----------                 -------   -------
  Total            5,994,396  6,037,395      6.27        89,241    90,964       7.74
 Average
  Maturity                               4 yrs. 1 mo.                       2 yrs. 1 mo.
Obligations of
 State and
 Political
 Subdivisions
 Within one year      90,652     91,461      7.53            --        --         --
 One to five
  years              157,653    162,456      7.89            --        --         --
 Five to 10
  years              100,725    105,162      8.09            --        --         --
 After 10 years       80,790     83,922      8.02            --        --         --
                  ---------- ----------                 -------   -------
  Total              429,820    443,001      7.89            --        --         --
 Average
  Maturity                               5 yrs. 3 mos.
Other(/3/)
 Within one year     240,659    240,890      6.58         1,704     1,664       9.61
 One to five
  years            1,280,833  1,289,507      6.85            --        --         --
 Five to 10
  years              217,948    220,458      5.48           149       148       6.41
 After 10 years      258,591    249,232      7.11            --        --         --
                  ---------- ----------                 -------   -------
  Total            1,998,031  2,000,087      6.70         1,853     1,812       9.35
 Average
  Maturity                               6 yrs. 3 mos.                      3 yrs. 2 mos.
Total Interest
 Earning
 Investments(/3/)
 Within one year   1,018,499  1,022,608      6.55        33,103    33,204       6.54
 One to five
  years            5,603,551  5,650,494      6.45        64,355    65,984       8.32
 Five to 10
  years            1,718,918  1,734,107      6.23           149       148       6.41
 After 10 years      358,699    352,900      7.29            --        --         --
                  ---------- ----------                 -------   -------
  Total            8,699,667  8,760,109      6.45        97,607    99,336       7.72
 Average
  Maturity                               4 yrs. 6 mos.                      2 yrs. 0 mos.
Federal Reserve
 Bank Stock,
 Federal Home
 Loan Bank Stock
 and Other
 Equity
 Investments         486,103    486,681      7.68            --        --         --
                  ---------- ----------                 -------   -------
 Total Portfolio  $9,185,770 $9,246,790      6.52       $97,607   $99,336       7.72
                  ========== ==========                 =======   =======
</TABLE>
 
(1) This exhibit excludes trading securities, which are reported at estimated
    fair value on the Consolidated Balance Sheet. Trading securities totaled
    $126,540,000, $70,536,000 and $31,361,000 at December 31, 1998, 1997, and
    1996, respectively.
(2) Taxable-equivalent basis.
(3) Maturities of asset-backed obligations are based on the remaining weighted
    average maturities.
-------------------------------------------------------------------------------
 
                                       8
<PAGE>
 
--------------------------------------------------------------------------------
 
SHORT-TERM BORROWINGS
(Dollars in Thousands)
 
<TABLE>
<CAPTION>
                       1998                      1997                      1996
             ------------------------- ------------------------- -------------------------
                              Average                   Average                   Average
               Amount   Rate  Maturity   Amount   Rate  Maturity   Amount   Rate  Maturity
             ---------- ----  -------- ---------- ----  -------- ---------- ----  --------
<S>          <C>        <C>   <C>      <C>        <C>   <C>      <C>        <C>   <C>
At Year End
Federal
 funds
 purchased
 and
  repurchase
 agreements  $2,087,373 4.60%  8 days  $2,127,443 5.49%  14 days $1,861,994 5.77%   8 days
Short-term
 FHLB
 advances       667,672 5.13  38 days   1,412,701 5.86  164 days    123,094 5.75  157 days
Treasury
 tax and
 loan notes     222,044 4.69   4 days     104,535 5.42    2 days    118,886 5.16    2 days
Commercial
 paper            3,025 5.23  29 days       1,510 5.25   15 days     19,405 5.45   17 days
Other
 short-term
 borrowings      22,546 5.84   4 days      32,351 6.32    2 days      9,295 6.52    4 days
             ----------                ----------                ----------
 Total
 Short-term
 Borrowings  $3,002,660 4.73  14 days  $3,678,540 5.64   71 days $2,132,674 5.74   16 days
             ==========                ==========                ==========
Average for
 the Year
Federal
 funds
 purchased
 and
 repurchase
 agreements  $2,051,219 5.13%          $2,085,927 5.32%          $1,446,828 5.29%
Short-term
 FHLB
 advances     1,052,433 5.61              718,697 5.73              117,705 6.36
Treasury
 tax and
 loan notes     157,074 5.20               87,513 5.25               78,909 5.20
Commercial
 paper            1,712 5.49               17,097 5.56               18,222 5.42
Other
 short-term
 borrowings      31,640 5.74               20,592 6.43                9,688 6.48
             ----------                ----------                ----------
 Total
 Short-term
 Borrowings  $3,294,078 5.29           $2,929,826 5.43           $1,671,352 5.37
             ==========                ==========                ==========
Maximum
 Month-End
 Balance
Federal
 funds
 purchased
 and
 repurchase
 agreements  $2,370,228                $2,579,789                $1,886,127
Short-term
 FHLB
 advances     1,472,114                 1,412,701                   130,239
Treasury
 tax and
 loan notes     402,733                   260,822                   439,181
Commercial
 paper            5,010                    24,800                    21,660
Other
 short-term
 borrowings      79,366                   102,833                    45,142
</TABLE>
 
--------------------------------------------------------------------------------
 
                                       9
<PAGE>
 
Item 2. Properties
 
   Mercantile and Mercantile Bank occupy 22 stories of the Mercantile Tower, a
35-story building owned by Mercantile Bank and located at Seventh and
Washington Streets in St. Louis, Missouri. Among the other properties owned by
Mercantile Bank are a four-story, 223,262 square foot data processing center
located at 1005 Convention Plaza, St. Louis, Missouri, and a four-story,
110,503 square foot banking facility located at 721 Locust Street, St. Louis,
Missouri. In addition, Mercantile Bank leases a two-story, 34,773 square foot
banking facility located at 10 North Hanley Road, Clayton, Missouri.
 
   Mercantile's subsidiaries own and lease other facilities in Missouri,
Illinois, Kansas, Iowa, Arkansas and Kentucky. See Note H to the Consolidated
Financial Statements included on page 66 in the Annual Report of the
Registrant to its Shareholders for the year ended December 31, 1998, which is
incorporated herein by reference.
 
Item 3. Legal Proceedings
 
   Mercantile and its subsidiaries are subject to various legal actions and
proceedings in the normal course of business, some of which involve
substantial claims for compensatory or punitive damages. Although litigation
is subject to many uncertainties and the ultimate exposure with respect to
these matters cannot be ascertained, management does not believe that the
final outcome of any known or threatened litigation will have a material
adverse effect on the financial condition of Mercantile.
 
Item 4. Submission of Matters to a Vote of Security Holders
 
   None.
 
Item 4a. Executive Officers of the Registrant
 
   See Part III, Item 10.
 
                                      10
<PAGE>
 
                                    PART II
 
Item 5. Market for the Registrant's Common Equity and Related Stockholder
Matters
 
   Information concerning the Common Stock of the Registrant, included on page
85 in the Annual Report of the Registrant to its Shareholders for the year
ended December 31, 1998, is incorporated herein by reference.
 
Item 6. Selected Financial Data
 
   Selected Financial Data, included as Exhibit 3 on page 27 in the Annual
Report of the Registrant to its Shareholders for the year ended December 31,
1998, is incorporated herein by reference.
 
Item 7. Management's Discussion and Analysis of Financial Condition and
Results of Operations
 
   Management's Discussion and Analysis of Financial Condition and Results of
Operations, included on pages 25 through 52 of the Annual Report of the
Registrant to its Shareholders for the year ended December 31, 1998, is
incorporated herein by reference.
 
Item 7a. Quantitative and Qualitative Disclosures About Market Risk
 
   Quantitative and Qualitative Disclosures About Market Risk, included as
Exhibit 6 on page 32 and under the Section entitled "Interest Rate
Sensitivity" on page 31 of the Annual Report of the Registrant to its
Shareholders for the year ended December 31, 1998, is incorporated herein by
reference.
 
Item 8. Financial Statements and Supplementary Data
 
   The following consolidated financial statements, included in the Annual
Report of the Registrant to its Shareholders for the year ended December 31,
1998, are incorporated herein by reference.
 
<TABLE>
<CAPTION>
                                                                  Annual Report
Statement                                                           Reference
---------                                                         -------------
 
<S>                                                               <C>
Independent Auditors' Report.                                      Page 53
Consolidated Statement of Income--Years ended December 31, 1998,
 1997 and 1996.                                                    Page 54
Consolidated Balance Sheet--December 31, 1998, 1997 and 1996.      Page 55
Consolidated Statement of Changes in Shareholders' Equity--Years
 ended December 31, 1998, 1997 and 1996.                           Page 56
Consolidated Statement of Cash Flows--Years ended December 31,
 1998, 1997 and 1996.                                              Page 57
Consolidated Statement of Comprehensive Income                     Page 58
Notes to Consolidated Financial Statements.                        Pages 59-79
</TABLE>
 
   Selected Quarterly Financial Data, included as Exhibit 20 on page 52 in the
Annual Report of the Registrant to its Shareholders for the year ended
December 31, 1998, is incorporated herein by reference.
 
Item 9. Changes in and Disagreements with Accountants on Accounting and
Financial Disclosure
 
   Not applicable.
 
                                   PART III
 
Item 10. Directors and Executive Officers of the Registrant
 
   Information regarding directors is contained in "Election of Directors" and
"Beneficial Ownership of Stock by Management," included in the Registrant's
Proxy Statement for the 1999 Annual Meeting of Shareholders, which information
is incorporated herein by reference.
 
                                      11
<PAGE>
 
   The following is a list, as of February 26, 1999, of the names and ages of
the executive officers of Mercantile and all positions and offices with
Mercantile presently held by the person named. There is no family relationship
between any of the named persons.
 
<TABLE>
<CAPTION>
        Name        Age All Positions and Offices Held with Mercantile
        ----        --- ----------------------------------------------
 <C>                <C> <S>
 W.Randolph Adams    54 Senior Executive Vice President and Chief
                        Administrative Officer
 
 John Q. Arnold      54 Vice Chairman, Private Banking and Investments
 Jon W. Bilstrom     52 General Counsel and Secretary
 John P. Dubinsky    55 Chairman, President and Chief Executive Officer,
                        Mercantile Bank National  Association
 John R. Elmore      42 President and Chief Executive Officer, Mercantile
                        Credit Corp., Inc.
 Arthur G. Heise     50 Senior Vice President and Auditor
 Thomas H. Jacobsen  59 Chairman of the Board, President and Chief Executive
                        Officer
 Stephen F. Milstid  48 Vice Chairman--Operations, Mercantile Bank National
                        Association
 John W. McClure     53 Vice Chairman and Chief Financial Officer
 Michael T. Normile  49 Senior Vice President, Finance and Control
</TABLE>
 
   The executive officers were appointed by and serve at the pleasure of the
Board of Directors of Mercantile. Messrs. Adams, Arnold, Bilstrom, Heise,
Jacobsen, Milstid, McClure and Normile have served as executive or senior
officers of either Mercantile or Mercantile Bank for at least the last five
years. Mr. Dubinsky served as President and Chief Executive Officer at Mark
Twain Bancshares, Inc. prior to joining Mercantile in April of 1997. Mr.
Elmore served as President of Mercantile Bank of Lawrence from 1990 until
starting in his new position in 1998.
 
   Information regarding compliance with Section 16 of the Securities and
Exchange Act of 1934, as amended, is contained in "Compliance with Section
16(a) of the Exchange Act," included in the Registrant's Proxy Statement for
the 1999 Annual Meeting of Shareholders, which information is incorporated
herein by reference.
 
Item 11. Executive Compensation
 
   Information regarding executive compensation is contained in "Compensation
of Executive Officers," included in the Registrant's Proxy Statement for the
1999 Annual Meeting of Shareholders, which is incorporated herein by
reference.
 
Item 12. Security Ownership of Certain Beneficial Owners and Management
 
   Information regarding security ownership of certain beneficial owners and
management is contained in "Voting Securities and Principal Holders Thereof"
and "Beneficial Ownership of Stock by Management," included in the
Registrant's Proxy Statement for the 1999 Annual Meeting of Shareholders,
which is incorporated herein by reference.
 
Item 13. Certain Relationships and Related Transactions
 
   Information regarding certain relationships and related transactions is
contained in "Interest of Management and Others in Certain Transactions,"
included in the Registrant's Proxy Statement for the 1999 Annual Meeting of
Shareholders, which is incorporated herein by reference.
 
 
                                      12
<PAGE>
 
                                    PART IV
 
Item 14. Exhibits, Financial Statement Schedules, and Reports on Form 8-K
 
    (a) (1) Financial Statements: Incorporated herein by reference, are listed
in Item 8 hereof.
 
     (2) Financial Statement Schedules: None.
 
     (3) Exhibits: See Exhibit Index at page 17 hereof.
 
    (b) Reports on Form 8-K
 
     Registrant filed a Current Report on Form 8-K on October 7, 1998, as
     previously disclosed in the Quarterly Report on Form 10-Q for the
     quarter ended September 30, 1998. That 8-K, under Item 5, contained
     supplemental consolidated financial statements for the years ended
     December 31, 1997, 1996 and 1995. Said statements restated Registrant's
     historical consolidated financial statements for those years to reflect
     the acquisitions of Firstbank of Illinois Co. ("Firstbank") and CBT
     Corporation ("CBT") on July 1, 1998. The Firstbank and CBT acquisitions
     were accounted for under the pooling-of-interests method of accounting.
     Registrant also filed Unaudited Interim Consolidated Financial
     Statements restating the Registrant's historical consolidated financial
     statements for the Firstbank and CBT transactions: 1) as of and for the
     three month periods ended March 31, 1998 and 1997; and 2) as of June 30,
     1998 and 1997, and for the three and six month periods ended June 30,
     1998 and 1997.
 
     Under Item 7, Registrant filed the consent of KPMG Peat Marwick LLP to
     incorporation by reference of its report on the Supplemental Financial
     Statements into pending registration statements of the Registrant.
 
     The October 7, 1998 Form 8-K included the financial statements, notes
     and auditor's report listed below:
 
       Independent Auditor's Report of KPMG Peat Marwick LLP dated October
       7, 1998.
 
       Supplemental Consolidated Statement of Income for the years ended
       December 31, 1997, 1996 and 1995.
 
       Supplemental Consolidated Balance Sheet as of December 31, 1997, 1996
       and 1995.
 
       Supplemental Consolidated Statement of Changes in Shareholders'
       Equity for the years ended December 31, 1997, 1996 and 1995.
 
       Supplemental Consolidated Statement of Cash Flows for the years ended
       December 31, 1997, 1996 and 1995.
 
       Notes to Supplemental Consolidated Statements.
 
       Supplemental Interim Consolidated Statement of Income (Unaudited) for
       the three months ended March 31, 1998 and 1997.
 
       Supplemental Interim Consolidated Balance Sheets (Unaudited) as of
       March 31, 1998 and 1997.
 
       Supplemental Interim Consolidated Statement of Changes in
       Shareholders' Equity (Unaudited) for the three months ended March 31,
       1998 and 1997.
 
       Supplemental Interim Consolidated Statement of Cash Flows (Unaudited)
       for the three months ended March 31, 1998 and 1997.
 
                                      13
<PAGE>
 
       Supplemental Interim Consolidated Statement of Comprehensive Income
       (Unaudited) for the three months ended March 31, 1998 and 1997.
 
       Supplemental Interim Consolidated Statement of Income (Unaudited) for
       the three months and six months ended June 30, 1998 and 1997.
 
       Supplemental Interim Consolidated Balance Sheets (Unaudited) as of
       June 30, 1998 and 1997.
 
       Supplemental Interim Consolidated Statement of Changes in
       Shareholders' Equity (Unaudited) for the six months ended June 30,
       1998 and 1997.
 
       Supplemental Interim Consolidated Statement of Cash Flows (Unaudited)
       for the six months ended June 30, 1998 and 1997.
 
       Supplemental Interim Consolidated Statement of Comprehensive Income
       (Unaudited) for the three months and six months ended June 30, 1998
       and 1997.
 
                                      14
<PAGE>
 
                                  SIGNATURES
 
   Pursuant to the requirements of Section 13 of the Securities Exchange Act
of 1934, the Registrant has duly caused this report to be signed on its behalf
by the undersigned, thereunto duly authorized.
 
                                          MERCANTILE BANCORPORATION INC.
                                          (Registrant)
 
 
 
                                                /s/ Thomas H. Jacobsen
Date: March 26, 1999                      By: _________________________________
                                                    Thomas H. Jacobsen
                                             Chairman of the Board, President,
                                                Chief Executive Officer and
                                                         Director
 
                               POWER OF ATTORNEY
 
   We, the undersigned officers and directors of Mercantile Bancorporation
Inc., hereby severally and individually constitute and appoint Thomas H.
Jacobsen and John W. McClure, and each of them, the true and lawful attorneys
and agents of each of us to execute in the name, place and stead of each of us
(individually and in any capacity stated below) any and all amendments to this
Annual Report on Form 10-K and all instruments necessary or advisable in
connection therewith and to file the same with the Securities and Exchange
Commission, each of said attorneys and agents to have the power to act with or
without the others and to have full power and authority to do and perform in
the name and on behalf of each of the undersigned every act whatsoever
necessary or advisable to be done in the premises as fully and to all intents
and purposes as any of the undersigned might or could do in person, and we
hereby ratify and confirm our signatures as they may be signed by our said
attorneys and agents or each of them to any and all such amendments and
instruments.
 
   Pursuant to the requirements of the Securities Exchange Act of 1934, this
report has been signed below by the following persons on behalf of the
Registrant and in the capacities and on the dates indicated.
 
<TABLE>
<CAPTION>
             Signature                           Title                    Date
             ---------                           -----                    ----
 
 
<S>                                  <C>                           <C>
     /s/ Thomas H. Jacobsen          Chairman of the Board,          March 26, 1999
____________________________________  President and Chief
        (Thomas H. Jacobsen)          Executive Officer
    Principal Executive Officer
 
      /s/ John W. McClure            Vice Chairman, Chief            March 18, 1999
____________________________________  Financial Officer
         (John W. McClure)
    Principal Financial Officer
 
     /s/ Michael T. Normile          Senior Vice President,          March 19, 1999
____________________________________  Finance and Control
        (Michael T. Normile)
    Principal Accounting Officer
 
     /s/ Richard E. Beumer                     Director              March 16, 1999
____________________________________
        (Richard E. Beumer)
 
      /s/ Harry M. Cornell                     Director              March 15, 1999
____________________________________
      (Harry M. Cornell, Jr.)
</TABLE>
 
                                      15
<PAGE>
 
<TABLE>
<CAPTION>
             Signature                           Title                    Date
             ---------                           -----                    ----
 
<S>                                  <C>                           <C>
      /s/ Dr. Henry Givens                     Director              March 15, 1999
____________________________________
      (Dr. Henry Givens, Jr.)
 
      /s/ William A. Hall                      Director              March 16, 1999
____________________________________
         (William A. Hall)
 
      /s/ Cinda A. Hallman                     Director              March 15, 1999
____________________________________
         (Cinda A. Hallman)
 
      /s/ Frank Lyon, Jr.                      Director              March 15, 1999
____________________________________
         (Frank Lyon, Jr.)
 
      /s/ Robert W. Murray                     Director              March 23, 1999
____________________________________
         (Robert W. Murray)
 
      /s/ Harvey Saligman                      Director              March 16, 1999
____________________________________
         (Harvey Saligman)
 
      /s/ Craig D. Schnuck                     Director              March 26, 1999
____________________________________
         (Craig D. Schnuck)
 
      /s/ Alvin J. Siteman                     Director              March 16, 1999
____________________________________
         (Alvin J. Siteman)
 
     /s/ Patrick T. Stokes                     Director              March 22, 1999
____________________________________
        (Patrick T. Stokes)
 
       /s/ John A. Wright                      Director              March 14, 1999
____________________________________
          (John A. Wright)
</TABLE>
 
                                       16
<PAGE>
 
                                 EXHIBIT INDEX
 
<TABLE>
<CAPTION>
 Exhibit No.                          Description
 -----------                          -----------
 <C>         <S>                                                            <C>
 No. 3-1(a)  Restated Articles of Incorporation of the Registrant, as
             amended and currently in effect, filed as Exhibit 3-1(a) to
             Registrant's Quarterly Report on Form 10-Q for the quarter
             ended March 31, 1998 (Commission File No. 1-11792), are
             incorporated herein by reference.
 No. 3-1(b)  Certificate of Designation, Preferences and Rights of Series
             B Junior Participating Preferred Stock of the Registrant
             filed as Exhibit 3-1(b) to Registrant's Quarterly Report on
             Form 10-Q for the quarter ended June 30, 1998 (Commission
             File No. 1-11792), is incorporated herein by reference.
 No. 3-2     By-Laws of the Registrant, as amended and currently in
             effect, filed as Exhibit 3.2 to Amendment No. 2 to
             Registrant's Registration Statement on Form S-4 (No. 333-
             17757), are incorporated herein by reference.
 No. 4-1     Form of Indenture Regarding Subordinated Securities between
             the Registrant and The First National Bank of Chicago as
             Trustee, filed on March 31, 1992 as Exhibit 4.1 to
             Registrant's Report on Form 8-K dated September 24, 1992
             (Commission File No. 1-11792), is incorporated herein by
             reference.
 No. 4-2     Rights Agreement dated as of May 20, 1998, between
             Registrant and Harris Trust and Savings Bank, as Rights
             Agent (including as an exhibit thereto the form of Rights
             Certificate) filed as Exhibit 4-2 to the Registrant's
             Quarterly Report on Form 10-Q for the quarter ended June 30,
             1998 (Commission File No. 1-11792), is incorporated herein
             by reference.
 No. 4-3     Form of Indenture Regarding Senior Debt Securities, filed as
             Exhibit 4.1 to Registrant's Registration Statement on Form
             S-3 (No. 333-25775), is incorporated herein by reference.
 No. 4-4     Form of Indenture Regarding Subordinated Debt Securities,
             filed as Exhibit 4.2 to Registrant's Registration Statement
             on Form S-3 (No. 333-25775), is incorporated herein by
             reference.
 No. 4-5     Indenture, dated February 4, 1997; First Supplemental
             Indenture, dated February 4, 1997, and Supplemental
             Indenture of First Supplemental Indenture, dated May 22,
             1997, between the Company, as issuer, and The Chase
             Manhattan Bank, as Indenture Trustee, filed as Exhibits 4.5,
             4.6 and 4.12, respectively, to the Company's Registration
             Statement on Form S-4 (No. 333-25131), are incorporated
             herein by reference.
 No. 10-1    The Mercantile Bancorporation Inc. 1987 Stock Option Plan,
             as amended, filed as Exhibit 10-3 to Registrant's Report on
             Form 10-K for the year ended December 31, 1989 (Commission
             File No. 1-11792), is incorporated herein by reference.*
 No. 10-2    The Mercantile Bancorporation Inc. Amended and Restated
             Executive Incentive Compensation Plan, filed as Annex H to
             Registrant's definitive Proxy Statement for the 1997 Annual
             Meeting of Shareholders (Commission File No. 1-11792), is
             incorporated herein by reference.*
 No. 10-3    The Mercantile Bancorporation Inc. Employee Stock Purchase
             Plan, filed as Exhibit 10-7 to Registrant's Annual Report on
             Form 10-K for the year ended December 31, 1989 (Commission
             File No. 1-11792), is incorporated herein by reference.*
 No. 10-4    The Mercantile Bancorporation Inc. 1991 Employee Incentive
             Plan, filed as Exhibit 10-7 to Registrant's Annual Report on
             Form 10-K for the year ended December 31, 1990 (Commission
             File No. 1-11792), is incorporated herein by reference.*
 No. 10-5    Amendment Number One to the Mercantile Bancorporation Inc.
             1991 Employee Incentive Plan, filed as Exhibit 10-6 to
             Registrant's Annual Report on Form 10-K for the year ended
             December 31, 1994 (Commission File No. 1-11792), is
             incorporated herein by reference.*
 No. 10-6    The Mercantile Bancorporation Inc. Amended and Restated
             Stock Incentive Plan, filed as Annex G to Registrant's
             definitive Proxy Statement for the 1997 Annual Meeting of
             Shareholders (Commission File No. 1-11792), is incorporated
             herein by reference.*
 No. 10-7    The Mercantile Bancorporation Inc. 1994 Stock Incentive Plan
             for Non-Employee Directors, filed as Appendix E to
             Registrant's definitive Proxy Statement for the 1994 Annual
             Meeting of Shareholders (Commission File No. 1-11792), is
             incorporated herein by reference.*
</TABLE>
 
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<PAGE>
 
<TABLE>
<CAPTION>
 Exhibit No.                          Description
 -----------                          -----------
 <C>         <S>                                                            <C>
 No. 10-8    The Mercantile Bancorporation Inc. Amended and Restated
             Voluntary Deferred Compensation Plan, filed as Exhibit 10.1
             to Registrant's Registration Statement on Form S-8 (No. 333-
             47713), is incorporated herein by reference.*
 No. 10-9    Mercantile Bancorporation Inc. Supplemental Retirement Plan,
             filed as Exhibit 10-12 to Registrant's Annual Report on Form
             10-K for the year ended December 31, 1992 (Commission File
             No. 1-11792), is incorporated herein by reference.*
 No. 10-10   Mercantile Bancorporation Inc. Voluntary Deferred
             Compensation Plan for Non-Employee Affiliate Directors and
             Advisory Directors, filed as Exhibit 10.3 to Registrant's
             Registration Statement on Form S-8 (No. 333-47713), is
             incorporated herein by reference.*
 No. 10-11   Mercantile Bancorporation Inc. Amended and Restated Stock
             Incentive Plan for Non-Employee Directors, filed as Exhibit
             10.2 to Registrant's Registration Statement on Form S-8 (No.
             333-47713), is incorporated herein by reference.*
 No. 10-12   Employment Agreement for Thomas H. Jacobsen, as amended and
             restated, filed as Exhibit 10.9 to Registrant's Annual
             Report on Form 10-K for the year ended December 31, 1997
             (Commission File No. 1-11792), is incorporated by reference
             herein.*
 No. 10-13   Form of Change of Control Employment Agreement for John W.
             McClure, W. Randolph Adams, John Q. Arnold and Certain Other
             Executive Officers, filed as Exhibit 10-10 to Registrant's
             Annual Report on Form 10-K for the year ended December 31,
             1989 (Commission File No. 1-11792), is incorporated herein
             by reference.*
 No. 10-14   Employment Agreement for Alvin J. Siteman, dated November
             18, 1996, filed as Exhibit 10.3 to Registrant's Report on
             Form 10-Q for the quarter ended March 31, 1997 (Commission
             File No. 1-11792), is incorporated herein by reference.*
 No. 10-15   Employment Agreement for John P. Dubinsky, dated October 27,
             1996, filed as Exhibit 10.4 to Registrant's Report on Form
             10-Q for the quarter ended March 31, 1997 (Commission File
             No. 1-11792), is incorporated herein by reference.*
 No. 13      Excerpts from Annual Report of the Registrant to its
             Shareholders for the year ended December 31, 1998.
 No. 21      Subsidiaries of the Registrant as of February 26, 1999.
 No. 23      Consent of KPMG LLP.
 No. 24      Power of Attorney (on signature page).
 No. 27      Financial Data Schedule (December 31, 1998).
</TABLE>
--------
   *Management contract or compensatory plan or arrangement
 
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