<PAGE>
 
                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549
                                  FORM 10-K/A

               Annual Report Pursuant to Section 13 or 15(d) of
                      The Securities Exchange Act of 1934

[X] ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
    SECURITIES EXCHANGE ACT OF 1934 (FEE REQUIRED)
    For the fiscal year ended     December 31, 1997
                              ------------------------------

[ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
    SECURITIES EXCHANGE ACT OF 1934 (NO FEE REQUIRED)
    For the transition period from __________ to ___________

    Commission file number 0-14468.
                           --------

                       First Oak Brook Bancshares, Inc.
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            (Exact name of registrant as specified in its charter)

           Delaware                                           36-3220778
-------------------------------                       --------------------------
(State or other jurisdiction of                            (I.R.S. Employer
incorporation or organization)                           Identification No.)

1400 Sixteenth Street, Oak Brook, Illinois                      60523
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(Address of principal executive offices)                     (Zip Code)

Registrant's telephone number, including area code (630) 571-1050
                                                   --------------

Securities registered pursuant to Section 12(b) of the Act:  None
                                                             ----

Securities registered pursuant to Section 12(g) of the Act:
                      Class A Common Stock ($2 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 and Exchange Act of 1934
during the preceding 12 months (or for such shorter period that the registrant
was required to file such reports), 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 ((S)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. [X]

The aggregate market value of the voting stock held by non-affiliates of the
registrant as of March 17, 1998 was:  $111,163,119 based upon the last sales
price of the registrant's Class A Common stock at $48.125 per share as reported
by the National Association of Securities Dealers Automated Quotation System.

The number of shares outstanding of each of the registrant's classes of common
stock as of March 17, 1998: 1,461,665 shares of Common Stock and 1,887,240
shares of Class A Common Stock.

Documents incorporated by reference:  Portions of the Company's Annual Report to
Shareholders for the fiscal year ended December 31, 1997, and Proxy Statement
for its 1998 Annual Meeting of Shareholders to be filed on or about April 1,
1998 are incorporated by reference into Parts I., II. and III. hereof, to the
extent indicated in the Form 10-K Cross-Reference Index.

This amended Form 10-K has been filed to correct a typographical error made in 
Item 7a of the 1997 Form 10-K filed on March 31, 1998. Item 7a is on pages 16-17
of the 1997 Annual Report incorporated by reference as Exhibit 13.
<PAGE>
 
FINANCIAL REVIEW
 
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INTEREST RATE SENSITIVITY
 
Interest rate risk arises when the maturity or repricing of assets differs sig-
nificantly from the maturity or repricing of liabilities. The Company's finan-
cial results could be affected by changes in market interest rates such as the
prime rate, LIBOR and treasury yields as well as competitive pressures for re-
tail deposit products. The objective of interest rate risk management is to
provide the maximum levels of net interest income while maintaining acceptable
levels of interest rate risk and liquidity risk. A number of measures are used
to monitor and manage interest rate risk, including income simulation and in-
terest sensitivity (gap) analyses.
 
An income simulation model is the primary tool used to assess the direction and
magnitude of changes in net interest income resulting from changes in interest
rates. The model incorporates management assumptions regarding the level of
interest rate or balance changes on indeterminate maturity deposit products
(passbook savings, money market, NOW and demand deposits) for a given level of
market rate changes. These assumptions are developed through historical analy-
sis. Additionally, changes in prepayment behavior of the mortgage related as-
sets in each rate environment are captured using estimates of prepayment speeds
for the portfolios. Other assumptions in the model include, cash flows and ma-
turities of other financial instruments, changes in market conditions, loan
volumes and pricing, and customer preferences. These assumptions are inherently
uncertain and, as a result, the model cannot precisely estimate net interest
income or precisely predict the impact of higher or lower interest rates on net
interest
16
                                                First Oak Brook Bancshares, Inc.
<PAGE>
 
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income. Actual results will differ from simulated results due to timing, mag-
nitude and frequency of interest rate changes and changes in market conditions
and management strategies, among other factors.
 
The Company's policy objective is to limit the change in annual net interest
income to 10% from an immediate and sustained parallel change in interest
rates of 200 basis points. As of December 31, 1997, the Company had the fol-
lowing estimated net interest income sensitivity profile. The impact of
planned growth and anticipated new business activities is not factored into
the calculation.
 
<TABLE>
<CAPTION>
                     Immediate Change in Rates
<S>                  <C>           <C>
                          -200 bp       +200 bp
-------------------------------------------------
Net interest income
 Dollar change
  (in thousands)             $630       $(2,169)
 Percent change               2.3%         (7.9)%
</TABLE>
 
The table below presents a static gap analysis as of December 31, 1997 which
does not fully capture the true dynamics of interest rate changes including the
timing and/or degree of interest rate changes. While most of the asset
categories' rates change when certain independent indices (such as the prime
rate) change, the liability categories are repriced at the Company's discretion.
 
INTEREST RATE SENSITIVE POSITION
<TABLE>
<CAPTION>
                               1-90      91-180     181-365     Over 1
(Dollars in thousands)         days        days        days       year    Total
-------------------------------------------------------------------------------
<S>                        <C>        <C>         <C>         <C>      <C>
Rate sensitive assets:
 Interest-bearing deposits
  with banks               $    167   $      72   $      --   $ 10,000 $ 10,239
 Taxable securities          29,214      21,060      28,609    176,514  255,397
 Tax exempt securities          663          --       2,307     43,731   46,701
 Loans, net of unearned
  discount                  180,727      26,347      51,764    188,494  447,332
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  Total                    $210,771   $  47,479   $  82,680   $418,739 $759,669
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  Cumulative total         $210,771   $ 258,250   $ 340,930   $759,669
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Rate sensitive
 liabilities:
 Savings and NOW
  accounts/1/              $104,438   $   1,616   $   4,038   $ 55,948 $166,040
 Money market accounts       33,139          --          --         --   33,139
 Time deposits               86,526      58,780      65,830     63,642  274,778
 Short-term and long-term
  debt                       86,312          56       6,248     15,000  107,616
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  Total                    $310,415   $  60,452   $  76,116   $134,590 $581,573
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  Cumulative total         $310,415   $ 370,867   $ 446,983   $581,573
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Cumulative gap             $(99,644)  $(112,617)  $(106,053)  $178,096
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Cumulative gap to total
 assets ratio                (12.21)%    (13.80)%    (12.99)%
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</TABLE>
/1/The decay assumptions on savings and NOW accounts are based on historical
analysis and experience.
                                                                             17
First Oak Brook Bancshares, Inc.