<PAGE>

This statement is intended to satisfy the requirements for an annual disclosure
statement as contained in Section 350.4(a) of the Federal Deposit Insurance
Corporation regulations. This statement has not been reviewed, or confirmed for
accuracy or relevance, by the Federal Deposit Insurance Corporation.
--------------------------------------------------------------------------------

                      Securities and Exchange Commission
                            Washington, D.C. 20549

                                   Form 10-K/A

      [X]        Annual Report Pursuant to Section 13 or 15(d)
                    of the Securities Exchange Act of 1934
                  For the fiscal year ended December 31, 1999

                                      OR

      [_]      Transition Report Pursuant to Section 13 or 15(d)
                    of the Securities Exchange Act of 1934
               For the transition period from _______ to ______

                       Commission File Number:  0-17177

                               BSB BANCORP, INC.
           ---------------------------------------------------------
            (Exact name of registrant as specified in its charter)

                 Delaware                                   16-1327860
    ---------------------------------                 ---------------------
     (State or other jurisdiction of                    (I.R.S. Employer
      incorporation or organization)                   Identification No.)

 58-68 Exchange Street, Binghamton, New York                   13901
 -------------------------------------------             ----------------
  (Address of principal executive offices)                  (Zip Code)

      Registrant's telephone number, including area code: (607) 779-2492
  Securities registered pursuant to Section 12(b) of the Act:  Not applicable
  Securities registered pursuant to Section 12(g) of the Act:
                                       Common Stock, ($0.01 par value per share)
                                       -----------------------------------------
                                                       Title of class

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 [_]   No [X]

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 of Part III of this Form 10-K
or any amendment to this Form 10-K.  [_]

As of March  6, 2000, the aggregate value of the 10,245,842 shares of Common
Stock of the Registrant issued and outstanding on such date, excluding 852,013
shares held by all affiliates of the Registrant, was approximately $159,695,093.
This figure is based on the closing sales price of $17.00 per share of the
Registrant's Common Stock on March 6, 2000. For purposes of this calculation,
the shares held by directors and executive officers of the registrant have been
excluded because such persons may be deemed to be affiliates. This reference to
affiliate status is not necessarily a conclusive determination for other
purposes.

Number of shares of Common Stock outstanding as of March 6, 2000 - 10,245,842

                      DOCUMENTS INCORPORATED BY REFERENCE

    List hereunder the following documents incorporated by reference and the
Part of the Form 10-K into which the document is incorporated:

    (1)  Portions of the Registrant's Annual Report to Shareholders for the year
ended December 31, 1999 are incorporated by reference into Part II, Items 5 - 8
of this Form 10-K.

    (2) Portions of the definitive Proxy Statement to be filed within 120 days
after the end of the fiscal year, covered by this Report for the Registrant's
Annual Meeting of Shareholders to be held on April 24, 2000 are incorporated by
reference into Part III, Items 10 - 13 of this Form 10-K.

                   Exhibit Index appears on numbered page 28
<PAGE>

Amendment to Cover Page
-----------------------

          This amendment to the Form 10-K filed with the Securities and Exchange
Commission on March 29, 2000 by BSB Bancorp, Inc. (the "Company") is being filed
for the sole purpose of indicating that Item 405 of Regulation S-K disclosure
will be contained in the Definitive Proxy Statement of the Company.

<PAGE>

                                  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, as of March 30, 2000.



                        BSB BANCORP, INC.


                        By:  /s/ Rexford C. Decker
                             ------------------------
                             Rexford C. Decker
                             Senior Vice President and Chief Financial Officer