<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D. C. 20549
                                    Form 10-K

[X]  ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
     ACT OF 1934

                     For fiscal year ended December 31, 1997

                                       or

[ ]  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
     EXCHANGE ACT OF 1934

     For transition period from ______________to______________

                         Commission File Number 0-13655
                            SECURITY BANC CORPORATION
                          State of Incorporation: Ohio
                I.R.S. Employer Identification Number: 31-1133284
                            40 South Limestone Street
                     Springfield, Ohio 45502 (513) 324-6800

           Securities register pursuant to Section 12(g) of the Act:
                         Common Stock, $3.125 Par Value

Indicate by check mark whether the registrant (1) has filed all reports required
                  to be filed by Section 13 or 15(d) 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 (229.405 of this chapter) 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 or any amendment to this Form 10-K.
         Yes  X   No
             ---     ---

The aggregate market value of the voting stock held by non-affiliates of the
Registrant was $330,574,437.00 as of January 10, 1998.

The number of shares outstanding of the Registrant's common stock, $3.125 par
value per share as of January 21, 1998 was 6,065,586 shares.

DOCUMENTS INCORPORATED BY REFERENCE
Portions of the Annual Shareholder's Report for the year ended December 31, 1997
are incorporated by reference into Parts I and II.

Portions of the Proxy Statement for the Annual Shareholder's Meeting to be held
April 21, 1998 are incorporated by reference into Part III.
<PAGE>   2
                   SECURITY BANC CORPORATION AND SUBSIDIARIES

<TABLE>
                                      INDEX
<CAPTION>
                                                                                         Page No.
                                                                                         --------
<S>                                                                                      <C>
PART I
         Item 1.  Business...........................................................    3 thru 17

         Item 2.  Properties.........................................................           18

         Item 3.  Legal Proceedings..................................................           19

         Item 4.  Submission of Matters to a Vote of Security Holders................           19

PART II
         Item 5.  Market for Registrant's Common Equity and Related Shareholder
                    Matters  ........................................................           19

         Item 6.  Selected Financial Data............................................           19

         Item 7.  Management's Discussion and Analysis of Financial Condition
                    and Results of Operations........................................           19

         Item 8.  Financial Statements and Supplementary Data........................           19

         Item 9.  Changes in and Disagreements with Accountants on Accounting
                    and Financial Disclosure.........................................           19

PART III
         Item 10. Directors and Executive Officers of The Registrant.................           20

         Item 11. Executive Compensation.............................................           20

         Item 12. Security Ownership of Certain Beneficial Owners and Management.....           21

         Item 13. Certain Relationships and Related Transactions.....................           21

PART IV
         Item 14. Exhibits, Financial Statement Schedules and Reports on Form 8-K....   21 thru 22

SIGNATURES...........................................................................           23
</TABLE>

                                       -2-
<PAGE>   3
PART I

ITEM 1.  BUSINESS

         Security Banc Corp. (Registrant or Company) was organized in 1985 under
         the laws of The State of Ohio. The Executive Office of the registrant
         is located in Springfield, Ohio. It is a Bank Holding Company as
         defined in the Bank Holding Company Act of 1956, as amended, and is
         registered as such with the Board of Governors of the Federal Reserve
         System. Registrant has three subsidiaries, The Security National Bank
         and Trust Co. (Security), Citizens National Bank (Citizens), and Third
         Savings and Loan Company, (Third).

         The Security National Bank and Trust Co. was organized under the
         statutes of The United States as the result of an agreement to merge
         The Guardian Bank of Springfield, Ohio, with and into The New Carlisle
         National Bank under the title of The Security National Bank. The
         agreement to merge was finalized and given approval by the Office of
         The Comptroller of the Currency on October 1, 1969. The Bank was
         granted the authority to act as a fiduciary as of May 30, 1978,
         thereby, changing the name of the Association to "The Security National
         Bank and Trust Co." The Bank's main office is located at 40 South
         Limestone Street, Springfield, Ohio.

         On September 30, 1996, the Company merged with CitNat Bancorp, Inc., a
         $140 million bank holding company headquartered in Ohio, in a
         transaction accounted for as a pooling of interest.

         On October 21, 1996, the Company acquired all of the outstanding shares
         of Third Financial Corporation for $41 million. The acquisition was
         accounted for using the purchase method of accounting.

         Security and Citizens are subject to primary supervision, examination,
         and regulation by The Comptroller of the Currency. Third is subject to
         primary supervision, examination, and regulation by The Office of
         Thrift Supervision. Security and Citizens are members of The Federal
         Reserve System and are subject to the applicable provisions of The
         Federal Reserve System and are subject to the applicable provisions of
         the Federal Reserve Act and Regulations. Deposits of the Company are
         insured by The Federal Deposit Insurance Corporation (FDIC) to the
         maximum extent permitted by law.

         Security was the parent of the Security Community Urban Redevelopment
         Corporation. The subsidiary was an Ohio Corporation organized in 1975
         and dissolved in 1997. It was organized solely to own Security's main
         office building. Presently, Security owns the Main Office building.

         All of the Company's banking centers are located in Champaign, Clark,
         Fayette, Greene, Madison and Miami Counties in the state of Ohio.

                                       -3-
<PAGE>   4
BUSINESS--Continued

As of December 31, 1997, the Company's consolidated total assets rounded to the
nearest thousand, were $839,605,000 including total loans of $562,005,000. On
that date, total deposits were $677,391,000 and capital accounts totaled
$108,736,000.

The Company's subsidiaries provide full service banking to individuals as well
as to industry and governmental subdivisions through each of its twenty-four
banking centers.

The Company's subsidiaries have made a strong impact on all the counties it
serves through a great variety of services, including personal checking accounts
and savings programs, certificates of deposit, the Money Market accounts, C/D's
and Individual Retirement Accounts.

A broad range of credit programs for all retail customers includes mortgage
loans, credit card banking under the VISA designation, installment loans, and
secured and unsecured personal loans.

The banking services provided to commercial customers and government include
maintenance of demand and time deposit accounts and certificates of deposit.
Available are all types of commercial loans, including loans under lines of
credit and revolving credit, term loans, real estate mortgage loans and other
specialized loans including accounts receivable financing. The Subsidiaries
further serve the requirements of large and small industrial and commercial
enterprises in the Springfield metropolitan area and elsewhere by providing
financial counseling, automated payroll programs, cash management, and other
automated services.

The subsidiaries' Commercial Banking Division is organized to serve the needs of
the corporate customers by handling business and commercial mortgages, corporate
deposits and other corporate financial services.

The Consumer Banking Divisions, which encompasses the Credit Card and
Installment Loan Departments, serves individual as well as corporate customers.
The Residential Mortgage Loan Departments provides conventional as well as
adjustable rate mortgage loans to individuals. Each Subsidiary manages the
investment of funds for their institution using U. S. Government and agency
securities, municipal (tax exempt) securities, as well as Federal Funds and
certificates of deposit of U. S. banks and savings and loans. Each Subsidiary,
in consultation with others, sets the rates on their liability products
including purchased federal funds.

Complete fiduciary services are available to individuals, charitable
institutions, commercial customers and government agencies through Security's
Trust Division. The Personal Trust Department serves as investment agent and
custodian for securities portfolios of individuals, as trustees for living and
testamentary trusts and as executor and administrator of probate estates. The
Corporate Trust Department serves as Trustee for corporate and municipal bond
issues, and as registrar for securities. The Institutional Services Department
provides employee benefit plan fund management for qualified retirement plans
and investment management and securities custody services for not-for-profit
institutions.

There are over a half dozen commercial banks in Springfield, Clark County and
adjoining counties, furnishing general banking services and thus providing
strong competition to the Company. The Company competes for deposits not only
with commercial banks in its area, but also with building and loan associations
and other non-bank competitors, such as brokerage houses. In addition to the
competition described above, the Company competes in various areas of service
offered to individuals, industry and government with Banks in Southwestern Ohio,
many of which possess greater financial resources than the Company.

                                       -4-
<PAGE>   5
BUSINESS--Continued

The earnings of the Company are affected by general economic conditions as well
as, by the monetary policies of the Federal Reserve Board. Such policies, which
have the effect of regulating the national supply of Bank reserves and Bank
credit, can have a major affect upon the source and cost of loanable and
investable funds and the rates of return earned on loans and investments. Among
the means available to the monetary authorities to influence the size and
distribution of Bank reserves are open market operations by the Board of
Governors of the Federal Reserve System, changes in cash reserve requirements
against member bank deposits, and limitations on interest rates which member
banks may pay on most time and savings deposits.

Material Changes and Developments
---------------------------------

There were no material changes or developments during 1997 in the business done
by the Company.

Regulation and Supervision
--------------------------

Security and Citizens, as national banks, are subject to regulation by the
Comptroller of the Currency, The Board of Governors of the Federal Reserve
System and The Federal Deposit Insurance Corporation. Third, as a savings and
loan, is subject to regulation by the Office of Thrift Supervision and The
Savings Association Insurance Fund. The Company and any subsidiaries which it
may hereafter have will be affiliates of the Company within the meaning of the
Federal Reserve Act. As affiliates, the Company and any such subsidiaries are
subject to certain restrictions on loans by the subsidiaries, on investments by
the subsidiaries in their stock or securities or on its taking such stock and
securities as collateral for loans to any borrower. The Company and any such
subsidiaries, as affiliates of the Company are also subject to certain
restrictions with respect to engaging in the underwriting and public sale and
distribution of securities. Neither the Company nor any such subsidiaries may,
for example, engage in such transactions with respect to securities of the
company unless such securities are registered under the Securities Act of 1993
or any exemption from such registration is available. In addition, any such
affiliates of the Bank will be subject to examination at the discretion of
supervisory authorities.

The Company, as a Bank Holding Company, is subject to the restrictions of the
Bank Holding Company Act of 1956 as amended. This Act first provides that the
acquisition of control of a bank is subject to the prior approval of the Board
of Governors of the Federal Reserve System. In the future, the Company will be
required to obtain the prior approval of the Federal Reserve Board before it may
acquire, for its individual account all, or substantially all, of the assets of
any bank, or acquire ownership or control of any voting securities of any Bank,
if after giving effect to such acquisition, the Company would own or control
more than 5% of the voting shares of such bank. The Act does not permit the
Federal Reserve Board to approve the acquisition by the Company or any
subsidiary for their own account, of any voting shares of, or interest in, or
all, or substantially all, of the assets, of any bank located in a state other
than Ohio, unless such acquisition is specifically authorized by the statutes of
the state in which such bank is located.

The Bank Holding Company Act limits the activities which may be engaged in by
the Company and its subsidiaries to ownership of banks and those activities
which the Federal Reserve Board has deemed or may in the future find, by order
of regulations, to be so closely related to the banking or managing or
controlling banks as to be a proper incident thereto.

                                       -5-
<PAGE>   6
BUSINESS--Continued

Those activities presently authorized by the Federal Reserve Board include the
following general activities: (1) the making or acquiring of loans or other
extensions of credit: (2) operating as an industrial bank, Morris Plan Bank, or
industrial loan company according to state law without the accepting of demand
deposits and without the making of commercial loans: (3) the servicing of loans
for any person: (4) performing certain trust functions: (5) acting with certain
limitations as investment or financial advisor: (6) leasing personal property
and equipment: (7) the making of equity and debt investments in projects or
corporations designated primarily to promote community welfare: (8) providing
bookkeeping and data processing services for the internal operations of the Bank
Holding Company and its Subsidiaries: and providing to others, data processing
and transmission services and facilities for banking, financial or related
economic data: (9) acting as insurance agent or broker under certain
circumstances and with respect to certain types of insurance: (10) acting as
underwriter for credit life insurance and credit accident and health insurance
which is directly related to extensions of credit by the Bank Holding Company
System: (11) providing limited courier services for the internal operations of
the Holding Company, for checks exchanged among banking institutions, and for
audit and accounting media of a banking or financial nature used in processing
such media: (12) providing management consulting advice to non-affiliated banks
under certain limitations; (13) the retail sale of money orders with a face
value of $1,000 or less, of travelers checks and of U. S. Savings Bonds: (14)
performing appraisals of real estate: (15) providing securities brokerage
services, (restricted to buying and selling securities solely as agent for
customers), related securities activities and incidental activities: (16)
underwriting and dealing in government obligations and money market instruments:
(17) foreign exchange advisory and transactional services: and (18) acting as
futures commission merchant. For details and limitations on these activities,
reference should be made to Regulation Y of the Federal Reserve Board, as
amended. Further, under the 1970 amendment of this Act and the regulations of
the Federal Reserve Board, the Company and its subsidiaries will be prohibited
from engaging in certain tie-in arrangements in connection with any extension of
credit or provisions of any property or service.

Employees
---------

As of December 31, 1997, there were no full time employees of the Registrant.
Affiliates of the Registrant had full time equivalent employees of 341 of whom
59 were officers.

Statistical Information
-----------------------

Pages 7 through 17 contain statistical information on the Company and its
subsidiaries.

                                       -6-
<PAGE>   7
BUSINESS--CONTINUED

Investment Portfolio

The following table sets forth the carrying amount of investment securities at
the dates indicated. (000s)

<TABLE>
<CAPTION>
                                                              December 31
                                                              -----------
                                                     1997         1996         1995
                                                     ----         ----         ----
<S>                                                <C>          <C>          <C>
Available for Sale Investments:
    U. S. Treasury                                 $116,011     $136,020     $128,185
    U. S. Government Agencies and Corporations       12,887       15,419       15,844
    Corporate Bonds                                     250        1,464        2,240
    Mortgage Backed Securities                          135        2,387            0
    Equity Securities                                   356          485        1,463
                                                   --------     --------     --------
Total Available for Sale Investments               $129,639     $155,775     $147,732
Held to Maturity Investments:
    U. S. Treasury                                 $      0     $      0     $    605
    State and Political Subdivisions                 13,262       28,530       32,517
    Mortgage Backed Securities                        3,484        4,010        1,468
    Federal Reserve Stock and Other                   2,794        2,668        1,539
                                                                --------     --------
Total Held to Maturity Investments                 $ 19,540     $ 35,208     $ 36,129
                                                   --------     --------     --------
Total Carrying Value of Investments                $149,179     $190,983     $183,861
                                                   ========     ========     ========
</TABLE>


The following table sets forth the maturities of debt securities at December 31,
1997 and the weighted average yields of such securities (calculated on the basis
of the cost and effective yields weighted for the scheduled maturity of each
security). Tax-equivalent adjustments (using a 35% rate) have been made in
calculating yields on obligations of state and political subdivisions. (000)s

<TABLE>
<CAPTION>
                                                                            Maturing
--------------------------------------------------------------------------------------------------------------------------------
                                                                 After One               After Five
                                            Within                 Within                But Within                 After
                                           One Year              Five Years              Ten Years                Ten Years
                                       Amount     Yield       Amount     Yield        Amount     Yield        Amount     Yield
                                       ------     -----       ------     -----        ------     -----        ------     -----
<S>                                    <C>         <C>       <C>          <C>         <C>       <C>           <C>        <C>
Available for Sale Investments:
    U. S. Treasury                     $11,796     5.59%     $104,215     5.82%       $    0        0%        $ 0.00         0%
    U. S. Govt. Agencies and Corp.       4,433     6.18%        7,456     6.07%          998     6.37%             0         0%
    Corporate Bonds                        250     6.61%            0        0%            0        0%             0         0%
    Mortgage Backed Securities               0        0%            0        0%            0        0%           135      5.89%

Held to Maturity Investments:
States and Political Subdivisions        7,734     8.77%        3,769     7.52%        1,699    10.29%            60     11.00%
Mortgage-backed Securities                  51     6.13%        1,076     7.32%           80     6.58%         2,277      6.98%
                                       -----------------------------------------------------------------------------------------
                                       $24,264     6.72%     $116,516     5.91%       $2,777     8.77%        $2,472      6.70%
</TABLE>

                                       -7-
<PAGE>   8
BUSINESS--CONTINUED


Types of Loans
--------------

The following table summarizes consolidated loans by major category for the five
years ending December 31. (000s)

<TABLE>
<CAPTION>
                                                              December 31
                                        1997         1996         1995         1994         1993
                                        ----         ----         ----         ----         ----
<S>                                   <C>          <C>          <C>          <C>          <C>     
       Commercial and Agriculture     $252,053     $212,046     $170,905     $166,116     $152,197
       Real Estate                     225,791      234,935      132,402      130,753      121,906
       Consumer                         84,161       93,787       93,263       98,129       75,322
                                      --------     --------     --------     --------     --------
       TOTAL LOANS                    $562,005     $540,768     $396,570     $394,998     $349,425
                                      ========     ========     ========     ========     ========
</TABLE>


Non-accrual loans totaled $3,417,000 and $4,123,000 as of December 31, 1997 and
1996 respectively.

                                       -8-
<PAGE>   9
BUSINESS--CONTINUED


The following table shows the maturity of loans (excluding those in non accrual
status) outstanding as of December 31, 1997. Also provided are the amounts due
after one year classified according to the sensitivity to changes in interest
rates. (000s)

<TABLE>
<CAPTION>
                                                                        MATURING
-----------------------------------------------------------------------------------------------------------
                                                 Within        After One But          After
                                               One Year    Within Five Years     Five Years           Total
<S>                                            <C>                  <C>            <C>             <C>     
Commercial, Ag                                 $114,501             $ 62,463       $ 19,006        $195,970
Real Estate-Construction                         10,861                2,200          1,190          14,251
All Other Loans                                  80,580              154,816        112,971         348,367
                                               --------             --------       --------        --------
Total Loans                                    $205,942             $219,479       $133,167        $558,588
                                               ========             ========       ========        ========

Loans maturing after one year with:
Fixed Interest  rate                                                $124,826       $131,875
Variable Interest                                                     94,653          1,292
                                                                    ========       ========
                                                                    $219,479       $133,167
                                                                    ========       ========
</TABLE>


RISK ELEMENTS
-------------

Interest on loans is normally accrued at the rate agreed upon at the time each
loan was negotiated. It is the Bank's policy to discontinue accrual of interest
on commercial and mortgage loans when there is a clear indication that the
borrower's cash flow may not be sufficient to meet payments as they become due.
When a consumer loan is uncollectable, the loan is charged off. If there is
collateral, it is secured and disposed of. In regards to paragraph 6i of SFAS
118, the amounts are immaterial and, therefore, not disclosed. The following
table presents data concerning loans at risk at the end of each period. (000s).

<TABLE>
<CAPTION>
                                   1997        1996         1995        1994        1993
                                   ----        ----         ----        ----        ----
<S>                              <C>         <C>          <C>         <C>         <C>   
Non-accrual loans                $3,417      $4,123       $2,772      $2,598      $2,229

Accruing loans past
   due 90 days or more           $1,537      $1,709       $1,543        $561        $245

Restructured loans                 $333           0            0           0           0

Other Real Estate owned            $258        $256            0           0           0
</TABLE>

                                      -9-
<PAGE>   10
BUSINESS--CONTINUED

Summary of Loan Loss Experience
-------------------------------

This table summarized the Company's loan loss experience for each of the five
years ended December 31 (000s)

<TABLE>
<CAPTION>
                                1997          1996         1995         1994          1993
                                ----          ----         ----         ----          ----
<S>                           <C>           <C>           <C>          <C>          <C>
Balance at Jan. 1:            $ 6,827       $ 5,336       $5,101       $4,364       $ 4,310
Acquired Allowance                  0          1285            0            0             4

Charge-offs
             Commercial         1,000          1091          248          144           995
             Real Estate            6             4            0           15             5
             Consumer           1,182           868          829          573           419
                              -------       -------       ------       ------       -------
                                2,188          1963        1,077          732         1,419


Recoveries
             Commercial            64            55           97          411           178
             Real Estate           19             0            0            0             0
             Consumer             232           239          265          214           241
                              -------       -------       ------       ------       -------
                                  315           294          362          625           419
                              -------       -------       ------       ------       -------

Net Charge-offs                (1,873)       (1,669)        (715)        (107)       (1,000)

Provision for loan losses       1,300          1875          950          844         1,050
                              -------       -------       ------       ------       -------

Balance at Dec. 31:           $ 6,254       $ 6,827       $5,336       $5,101       $ 4,364
                              =======       =======       ======       ======       =======


Net Charge offs
to average loans                 0.34%         0.39%        0.18%        0.03%         0.30%
</TABLE>

                                      -10-
<PAGE>   11
BUSINESS--Continued

Allowance for Loan Losses
-------------------------


The allowance for loan losses is established through charges to operations by a
provision for loan losses. Loans which are determined to be uncollectible are
charged against the allowance and subsequent recoveries, if any, are credited to
the allowance. The amount charged to operations is based on several factors.
These include the following:

         1.       Analytical reviews of the loan loss experience in relationship
                  to outstanding loans to determine an adequate allowance for
                  loan losses required for loans at risk.

         2.       A continuing review of problem or at risk loans and the
                  overall portfolio quality.

         3.       Regular examinations and appraisals of the loan portfolio
                  conducted by the Bank's examination staff and the banking
                  supervisory authorities.

         4.       Management's judgement with respect to the current and
                  expected economic conditions and their impact on the existing
                  loan portfolio.

The amount provided for loan losses exceeded actual net charge-offs by $573,000
in 1997, $206,000 in 1996 and $235,000 in 1995.

It is management's practice to review the allowance on a quarterly basis to
determine whether additional provisions should be made after considering the
factors noted above. Based on these procedures, management is of the opinion
that the allowance at December 31, 1997 of $6,254,000 is adequate.

                                      -11-
<PAGE>   12
BUSINESS --CONTINUED


This table shows allocation of the allowance for loan losses as of the end of
the last five years. (000s)

<TABLE>
<CAPTION>
                             12-31-97             12-31-96             12-31-95              12-31-94              12-31-93
                        ------------------   ------------------   ------------------   -------------------   -------------------
                               Percent of           Percent of           Percent of            Percent of            Percent of
                                Loans to             Loans to             Loans to              Loans to              Loans to
                        Amount Total Loans   Amount Total Loans   Amount Total Loans   Amount  Total Loans   Amount  Total Loans
                        ------ -----------   ------ -----------   ------ -----------   ------  -----------   ------  -----------
<S>                     <C>       <C>        <C>       <C>        <C>       <C>        <C>        <C>        <C>        <C> 
Commercial and
Agriculture             $1,757     45%       $1,730     39%       $1,075     43%       $1,683      42%       $1,170      44%

Real Estate                331     40%           24     44%           52     33%           52      33%           36      35%

Consumer                   816     15%          826     17%          771     24%          588      25%          303      21%

Additional Reserve
Allocated for current
loans                      757                2,057                1,178                1,280                 1,206

Unallocated              2,593                2,190                2,260                1,498                 1,649
                        ------               ------               ------               ------                ------
                        $6,254    100%       $6,827    100%       $5,336    100%       $5,101     100%       $4,364     100%
                        ======    ===        ======    ===        ======    ===        ======     ===        ======     ===
</TABLE>

                                      -12-
<PAGE>   13
BUSINESS--CONTINUED


Deposits
--------

Maturities of time certificates of deposits and other time deposits of $100,000
or more, outstanding at December 31, are summarized as follows: (000s)

                                                      1997           1996
                                                      ----           ----

        Three months or less                       $11,269        $21,041
        Over three months through twelve months     18,380         21,389
        Over one year thru five years               12,096         11,790
                                                    ------         ------
                                                   $41,745        $54,220
                                                   =======        =======

Return on Equity and Assets
---------------------------

The following table shows consolidated operating and capital ratios of the
company for each of the last three years:

                                          Year Ended December 31

For the Years                     1997              1996            1995
-------------                     ----              ----            ----

Return on Assets (A)              1.75%             1.92%           1.95%

Return on Equity (B)             13.92%            14.18%          14.91%

Dividend Payout Ratio (C)        37.24%            36.49%          34.60%

Equity to Assets Ratio (D)       12.55%            13.52%          13.07%

---------------------------

         (A)      net income divided by average total assets
         (B)      net income divided by average equity
         (C)      dividends declared per share divided by net income per share
         (D)      average equity divided by average total assets

                                      -13-
<PAGE>   14
BUSINESS--CONTINUED


Loan Commitments and Standby Letters of Credit

Loan commitments are made to accommodate the financial needs of our customers.
Letters of credit commit the Company to make payments on behalf of customers
when specific future events occur.

Both arrangements have credit risk essentially the same as that involved in
extending loans to customers and are subject to the Company's normal credit
policies. Collateral (e.g., securities, receivables, inventory, equipment) is
obtained based on Management's credit assessment of the customer.

Off-balance sheet items at December 31  (000s)

                                                       1997              1996
                                                       ----              ----
Unused Commitments

         Open end consumer lines                    $43,267           $45,221
         Other unused commitments                    81,231            70,140

         Letters of Credit                           $2,072            $1,452

                                      -14-
<PAGE>   15
BUSINESS--CONTINUED

<TABLE>
                                               SECURITY NATIONAL "NEXT FOUR QUARTERS"
                                                     ASSET/LIABILITY MANAGEMENT
                                                     STATIC GAP ANALYSIS (000S)
<CAPTION>
                              IMMEDIATELY ADJUSTABLE    END OF 3/98         END OF 6/98         END OF 9/98         END OF 12/98
                                RUNOFFS      RATE     RUNOFFS    RATE     RUNOFFS    RATE     RUNOFFS    RATE     RUNOFFS    RATE
                                -------      ----     -------    ----     -------    ----     -------    ----     -------    ----
<S>                            <C>         <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>  
Total Investment Securities           0      0.00%     11,632    5.75%      2,960   10.67%      1,017   11.50%          0    0.00%
Total Short Term Investment           0      0.00%          0    0.00%          0    0.00%          0    0.00%          0    0.00%
Net Loans                        52,198      9.24%     30,975    9.27%     25,782    8.84%     22,247    9.06%     19,210    8.68%
Total Earning Assets             52,198      9.24%     42,607    8.31%     28,742    9.03%     23,264    9.16%     19,210    8.68%
Total Non-Earning Assets          2,502      9.57%          0    0.00%          0    0.00%          0    0.00%          0    0.00%
Total Assets                     54,700      9.26%     42,607    8.31%     28,742    9.03%     23,264    9.16%     19,210    8.68%
Total Noninterest Bearing
Deposits                              1      0.00%          0    0.00%          0    0.00%          0    0.00%          0    0.00%
Total Interest Bearing
Deposits                        207,080      2.87%     26,482    4.86%     24,534    4.90%     21,307    5.27%     16,558    5.31%
Total Deposits                  207,081      2.87%     26,482    4.86%     24,534    4.90%     21,307    5.27%     16,558    5.31%
Total Other Interest Bearing
Liabilities                      30,636      5.13%          0    0.00%          0    0.00%          0    0.00%          0    0.00%
Total Other Liabilities               0      0.00%          0    0.00%          0    0.00%          0    0.00%          0    0.00%
Total Liabilities               237,717      3.16%     26,482    4.86%     24,534    4.90%     21,307    5.27%     16,558    5.31%
Total Equity Capital                  0      0.00%          0    0.00%          0    0.00%          0    0.00%          0    0.00%
Total Liabilities and Capital   237,717      3.16%     26,482    4.86%     24,534    4.90%     21,307    5.27%     16,558    5.31%
Interval GAP                   (183,016)               16,125               4,208               1,957               2,652     
Cumulative GAP                 (183,016)             (166,891)           (162,683)           (160,727)           (158,075)    
Interval GAP/Earning Assets                (36.75%)              3.20%               0.83%               0.39%               0.53%
Cumulative GAP/Earning Assets              (36.75%)            (33.55%)            (32.72%)            (32.33%)            (31.81%)
Interval Spread:  Earning Assets             6.08%               3.45%               4.13%               3.89%               3.37%
Interval Spread: Total Assets                6.10%               3.45%               4.13%               3.89%               3.37%
</TABLE>

                                      -15-
<PAGE>   16
BUSINESS--CONTINUED
<TABLE>
                                               CITIZENS NATIONAL "NEXT FOUR QUARTERS"
                                                     ASSET/LIABILITY MANAGEMENT
                                                     STATIC GAP ANALYSIS (000S)
<CAPTION>
                              IMMEDIATELY ADJUSTABLE    END OF 3/98         END OF 6/98         END OF 9/98         END OF 12/98
                                RUNOFFS      RATE     RUNOFFS    RATE     RUNOFFS    RATE     RUNOFFS    RATE     RUNOFFS    RATE
                                -------      ----     -------    ----     -------    ----     -------    ----     -------    ----
<S>                             <C>         <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>  
Total Investment Securities      1,500       5.05%      7,670     5.76%     2,250     5.93%     4,405    5.80%      5,782     5.73%
Total Short Term Investment     12,555       5.40%      2,200     5.92%         0     0.00%         0    0.00%        500     6.51%
Net Loans                       23,559       9.05%      4,228     8.89%     3,703     8.59%     7,410    8.34%      2,636     9.00%
Total Earning Assets            37,614       7.67%     14,098     6.72%     5,953     7.58%    11,815    7.39%      8,918     6.74%
Total Non-Earning Assets           232       8.81%          0     0.00%         0     0.00%         0    0.00%          0     0.00%
Total Assets                    37,846       7.68%     14,098     6.72%     5,953     7.58%    11,815    7.39%      8,918     6.74%
Total Noninterest Bearing
Deposits                             0       0.00%      2,500     0.00%       831     0.00%       831    0.00%        839     0.00%
Total Interest Bearing
Deposits                         8,120       2.32%     27,617     3.32%    20,476     4.05%    20,725    4.26%     13,629     3.56%
Total Deposits                   8,120       2.32%     30,117     3.05%    21,307     3.89%    21,556    4.09%     14,468     3.35%
Total Other Interest Bearing
Liabilities                        700       4.01%        603     4.42%         0     0.00%         0    0.00%          0     0.00%
Total Other Liabilities              0       0.00%          0     0.00%         0     0.00%         0    0.00%          0     0.00%
Total Liabilities                8,820       2.46%     30,720     3.07%    21,307     3.89%    21,556    4.09%     14,468     3.35%
Total Equity Capital                 0       0.00%          0     0.00%         0     0.00%         0    0.00%          0     0.00%
Total Liabilities and Capital    8,820       2.46%     30,720     3.07%    21,307     3.89%    21,556    4.09%     14,468     3.35%
Interval GAP                    29,026                (16,621)            (15,354)             (9,741)             (5,550)
Cumulative GAP                  29,026                 12,404              (2,950)            (12,691)            (18,241)
Interval GAP/Earning Assets                 22.69%              (11.10%)            (11.42%)            (7.01%)              (3.70%)
Cumulative GAP/Earning Assets               22.69%               11.58%               0.16%             (6.84%)             (10.55%)
Interval Spread:  Earning Assets             5.21%                3.38%               3.53%              3.14%                3.18%
Interval Spread: Total Assets                5.22%                3.65%               3.69%              3.30%                3.39%
</TABLE>

                                      -16-
<PAGE>   17
BUSINESS--CONTINUED
<TABLE>
                                                 THIRD SAVINGS "NEXT FOUR QUARTERS"
                                                     ASSET/LIABILITY MANAGEMENT
                                                     STATIC GAP ANALYSIS (000S)
<CAPTION>
                              IMMEDIATELY ADJUSTABLE    END OF 3/98         END OF 6/98         END OF 9/98         END OF 12/98
                                RUNOFFS      RATE     RUNOFFS    RATE     RUNOFFS    RATE     RUNOFFS    RATE     RUNOFFS    RATE
                                -------      ----     -------    ----     -------    ----     -------    ----     -------    ----
<S>                             <C>         <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>  
Total Investment Securities       1,385      6.18%         0     0.00%      1,001    6.11%        500    5.12%          0    0.00%
Total Short Term Investment           0      0.00%         0     0.00%          0    0.00%          0    0.00%          0    0.00%
Net Loans                        16,331      9.33%    11,051     9.24%      8,255    8.84%      8,135    8.59%     11,184    8.20%
Total Earning Assets             17,716      9.08%    11,051     9.24%      9,256    8.54%      8,635    8.39%     11,184    8.20%
Total Non-Earning Assets             60     10.77%         0     0.00%          0    0.00%          0    0.00%          0    0.00%
Total Assets                     17,776      9.09%    11,051     9.24%      9,256    8.54%      8,635    8.39%     11,184    8.20%
Total Noninterest Bearing
Deposits                              0      0.00%     1,504     0.00%        752    0.00%          0    0.00%          0    0.00%
Total Interest Bearing
Deposits                          2,091      5.75%     7,562     5.32%     14,555    5.26%     16,251    5.54%      9,453    5.67%
Total Deposits                    2,091      5.75%     9,066     4.43%     15,307    5.00%     16,251    5.54%      9,453    5.67%
Total Other Interest Bearing
Liabilities                      11,000      5.32%         0     0.00%          0    0.00%          0    0.00%          0    0.00%
Total Other Liabilities               0      0.00%         0     0.00%          0    0.00%          0    0.00%          0    0.00%
Total Liabilities                13,091      5.39%     9,066     4.43%     15,307    5.00%     16,251    5.54%      9,453    5.67%
Total Equity Capital                  0      0.00%         0     0.00%          0    0.00%          0    0.00%          0    0.00%
Total Liabilities and Capital    13,091      5.39%     9,066     4.43%     15,307    5.00%     16,251    5.54%      9,453    5.67%
Interval GAP                      4,685                1,985               (6,051)             (7,616)              1,731
Cumulative GAP                    4,685                6,670                  618              (6,998)             (5,267)
Interval GAP/Earning Assets                  3.21%               2.42%              (3.67%)             (5.28%)              1.20%
Cumulative GAP/Earning Assets                3.21%               5.63%               1.95%              (3.33%)             (2.13%)
Interval Spread:  Earning Assets             3.69%               3.93%               3.29%               2.84%               2.54%
Interval Spread: Total Assets                3.70%               4.81%               3.54%               2.84%               2.54%
</TABLE>

                                      -17-
<PAGE>   18
ITEM 2.  PROPERTIES
         The Security Banc Corporation is headquartered in Springfield, Ohio at
         40 South Limestone Street. The subsidiaries of the Company have 24
         banking offices located in Ohio. The Company owns 22 of the offices and
         the other two are leased. Additional information is contained in the
         Notes to Consolidated Financial Statements, Part IV, Item 14.

                                      -18-
<PAGE>   19
ITEM 3.  LEGAL PROCEEDINGS
         Registrant and its subsidiaries are not a party to any material legal
         proceedings.

ITEM 4.  SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS
         1.       To elect four directors of Class 1 to serve until the Annual
                  Meeting of Shareholders in 2001 or in the case of each
                  director until his successor is duly elected and qualified.

         2.       Adoption of Amendment to Article IV of the Company's Amended
                  Articles of Incorporation changing the number of authorized
                  shares of the Company's Common Stock from eleven million
                  (11,000,000) to eighteen million (18,000,000) shares, changing
                  the par value for each share to one dollar and fifty-six
                  twenty-five cents ($1.5625) which will permit the Board of
                  Directors to declare the subsequent two (2) for one (1) stock
                  split for each share owned.

         3.       Approval of the Corporation's 1998 Stock Option Plan.

         4.       To transact such other business as may properly come before
                  the Annual Meeting or any adjournments thereof.

PART II
ITEM 5.  MARKET FOR REGISTRANT'S COMMON EQUITY AND RELATED SHAREHOLDER MATTERS
         The common stock of the Corporation is traded on the over-the-counter
         market. Transfer agent and registrar is The Registrar and Transfer Co.,
         10 Commerce Drive, Cranford, NJ 07016. Common stock market prices and
         dividends on page 13 of the annual shareholders' report for the year
         ended December 31, 1997 is incorporated herein by reference.

ITEM 6.  SELECTED FINANCIAL DATA
         The information required by this item is incorporated herein by
         reference to the registrant's 1997 Annual Report to Shareholders
         attached to this filing as Exhibit 13.

ITEM 7.  MANAGEMENT'S DISCUSSION AN ANALYSIS OF FINANCIAL CONDITION
         AND RESULTS OF OPERATION The information required by this item is
         incorporated herein by reference to the registrant's 1997 Annual Report
         to Shareholders attached to this filing as Exhibit 13.

ITEM 8.  FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA
         The information required by this item is incorporated herein by
         reference to the registrant's 1997 Annual Report to Shareholders
         attached to this filing as Exhibit 13.

ITEM 9.  CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS ON ACCOUNTING AND
         FINANCIAL DISCLOSURE
         None

                                      -19-
<PAGE>   20
PART III

ITEM 10. DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT
         The information required by this item concerning Directors is
         incorporated herein by reference to the registrant's 1998 Proxy
         Statement.

Executive Officers
------------------

The name, age, and position of the Executive Officers of the Registrant as of
March, 1998 is listed below along with their business experience during the past
five years. Officers are appointed annually by the Board of Directors at the
meeting of Directors immediately following the Annual Meeting of Stockholders.

Name, Age, Position                Business Experience During Past Five Years
-------------------                ------------------------------------------

    Executive Officers
    ------------------

    Harry O. Egger, 58             Security National Bank and Trust Co.
    Chairman, President, CEO       President 1981 - 1996
                                   Chairman, CEO since 1-1-97

    J. William Stapleton, 45       Security National Bank and Trust Co.
    Executive Vice President/CFO   Vice President since 9-18-84
                                   Executive Vice President since 1-1-97

    William C. Fralick, 43         Security National Bank and Trust Co.
    Vice President                 Vice President since 12-31-84
                                   President since 1-1-97

    Glenda S. Greenwood, 42        Security National Bank and Trust Co.
    Vice President                 Director of Marketing since 12-29-80
                                   Vice President since 1-1-97

    Daniel M. O'Keefe, 53          Security National Bank and Trust Co.
    Vice President                 Vice President/Trust Officer since 1-80

ITEM 11. EXECUTIVE COMPENSATION
         The information required by this item is incorporated herein by
         reference to the registrant's 1998 Proxy Statement.

                                      -20-
<PAGE>   21
PART III

ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT
         The information required by this item is incorporated herein by
         reference to the Registrant's 1998 Proxy Statement.

ITEM 13. CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS
         The information required by this item is incorporated herein by
         reference to the Registrant's 1998 Proxy Statement.

PART IV

ITEM 14. EXHIBITS, FINANCIAL STATEMENT SCHEDULES, AND REPORTS ON
         FORM 8-K.
         a)      Document filed as part of the report

                 1.   FINANCIAL STATEMENTS

                      The following consolidated financial statements and report
                      of independent auditors of Security Banc Corporation,
                      included in the 1997 Annual Report to its shareholders for
                      the year ended December 31, 1997 are incorporated by
                      reference in Item 8.

                      Report of Independent Auditors

                      Consolidated Statement of Condition, December 31, 1997 and
                      1996

                      Consolidated Statement of Income for the Years Ending
                      December 31, 1997, 1996, and 1995

                      Consolidated Statement of Shareholders' Equity for the
                      Years Ending December 31, 1997, 1996, and 1995

                      Consolidated Statement of Cash Flows for the Years Ending
                      December 31, 1997, 1996, and 1995

                      Notes to Consolidated Financial Statements

                                      -21-
<PAGE>   22
PART IV

ITEM 14. EXHIBITS, FINANCIAL STATEMENT SCHEDULES, AND REPORTS ON FORM 8-K
         (CONT'D)
         a)    Document filed as part of the report

               2.    Schedules to the consolidated financial statements required
                     by Article 9 of Regulation S-X are not required under the
                     related instructions or are inapplicable, and therefore
                     have been omitted.

         (b)   Reports on Form 8-K - None


         (c)   Exhibits

               13 - Security Banc Corporation 1997 Annual Report

               23 - Consent of Independent Auditors

               27 - Financial Data Schedule

         (d)   Financial Statement Schedules - None

         Security Banc Corp. has the following subsidiaries:

               1.    Security National Bank and Trust Co.
               2.    Citizens National Bank
               3.    Third Savings and Loan Company

                                      -22-
<PAGE>   23
SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) 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.

                            SECURITY BANC CORPORATION
                  --------------------------------------------
                                  (Registrant)


By  /s/ Harry O. Egger
   -----------------------------------------------
Harry O. Egger, Chairman of the Board and Director
(Principal Executive Officer)


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.


/s/ Larry D. Ewald         3-17-98          /s/ Jane N. Scarff         3-17-98
---------------------------                 ---------------------------
Director   Larry D. Ewald                   Director   Jane N. Scarff


/s/ Richard E. Kramer      3-17-98          /s/ Thomas J. Veskauf      3-17-98
---------------------------                 ---------------------------
Director   Richard E. Kramer                Director   Thomas J. Veskauf


/s/ Chester L. Walthall    3-17-98                                     3-17-98
---------------------------                 ---------------------------
Director   Chester L. Walthall              Director


/s/ Larry E. Kaffenbarger  3-17-98                                     3-17-98
---------------------------                 ---------------------------
Director   Larry E. Kaffenbarger            Director


/s/ Robert A. Warren       3-17-98                                     3-17-98
---------------------------                 ---------------------------
Director   Robert A. Warren                 Director


/s/ Harry O. Egger         3-17-98          /s/ J. William Stapleton   3-17-98
---------------------------                 ---------------------------
Chairman of the Board,                      Executive Vice President and
President and CEO                           Chief Financial Officer
Harry O. Egger                              (Principal Financial Officer)
                                            J. William Stapleton

/s/ Thomas L. Miller       3-17-98
---------------------------
Vice President/Controller
Security National Bank
Thomas L. Miller

                                      -23-