<PAGE>


                                                                   EXHIBIT 10.15


                       SEPARATION AGREEMENT AND GENERAL RELEASE


         THIS SEPARATION AGREEMENT AND GENERAL RELEASE is made and entered into
as of this 6th day of September, 1996 by and between William E. Viklund (the
"Executive"), LONG ISLAND BANCORP, INC., a Delaware corporation (the
"Corporation"), and LONG ISLAND SAVINGS BANK, FSB, a federal stock savings bank
organized under the laws of the United States (the "Bank") (the Corporation and
the Bank are sometimes hereinafter referred to separately as a "Company" or
together as the "Companies").


                                  W I T N E S S T H:


         WHEREAS, the Executive has been employed by each of the Corporation
and the Bank as its President and Chief Operating Officer and in other
capacities; and

         WHEREAS, on September 6, 1996 the Executive ceased to be the President
and Chief Operating Officer of each of the Corporation and the Bank, ceased all
other officer and employee positions with the Companies and their respective
subsidiaries, and has agreed to resign his membership on the Boards of Directors
and all Committees of the Companies and their respective subsidiaries and
affiliates; and

         WHEREAS, the Executive and the Companies desire to settle fully and
finally all matters between them to date, including, but in no way limited to,
any issues that might arise out of the Executive's employment or the termination
of his employment;

         NOW, THEREFORE, in consideration of the mutual covenants and promises
contained herein, the parties hereto, intending to be legally bound hereby,
agree as follows:

         1.   EMPLOYMENT AGREEMENTS.  The Executive and the Companies agree
that the Executive's termination of employment shall constitute a termination
without "cause" as provided in section 6.4 of the Executive's employment
agreement dated as of September 19, 1994 with each of the Corporation and the
Bank (the "Employment Agreements"), and that each of the Employment Agreements
remains in full force and effect.  Except as provided in this Agreement, all
payments or other benefits to the Executive may be or become entitled and all
continuing obligations to which the Executive will be subject on account of his
termination of employment will be determined in accordance with the terms of the
Employment Agreements, except that the

<PAGE>

                                          2

period in section 6.13 of each Employment Agreement shall be a five (5) year
period.  The Executive shall be paid a fee equal to $375 per hour for time spent
on litigation matters involving either of the Companies as requested from time
to time by such Company.  Such payment shall be made within a reasonable period
of time after the performance of such services by the Executive.

         In addition, the Companies, notwithstanding anything to the contrary
in the MRP or the SIP (as these terms are defined below), agree to cause (a) the
accelerated vesting of an additional 4,025 shares of restricted common stock of
the Corporation granted to the Executive under the Bank's Management Recognition
and Retention Plan for Executive Officers (the "MRP"), and (b) the accelerated
exercisability of a portion of the Executive's non-qualified stock option grant
(as awarded to the Executive under the Corporation's 1994 Stock Incentive Plan
(the "SIP")) in respect of 13,455 underlying shares of the Corporation's common
stock.  In all other respects, the terms and provisions of the MRP and the SIP
shall govern any restricted stock or stock option awards granted to the
Executive.  Except as provided in the next paragraph, the Corporation represents
and agrees that the options that have been granted to the Executive under the
SIP which have vested prior to the date of this Agreement or whose vesting has
been accelerated pursuant to this Agreement are immediately exercisable.

         Also, the Companies, notwithstanding anything to the contrary in the
MRP or the SIP, agree to cause the modification of the exercisability schedule
for a portion of the Executive's non-qualified stock option grant (as awarded to
the Executive under the SIP) in respect of 7,000 underlying shares of the
Corporation's common stock to provide for the  exercisability of such portion
upon and after March 29, 1998 and an exercise period thereafter terminating at
the close of the Bank's business on September 29, 1999.

         Finally, the Bank shall cause the Bank's Deferred Pension Plan (the
"DPP") to provide that, in lieu of any other benefit thereunder, the Executive
shall receive a benefit thereunder per annum for ten years equal to $97,236 per
annum, payable in 40 equal quarterly installments commencing October 1, 1999.

         2.   ANNOUNCEMENT.  The parties agree that any announcement by either
of the Companies with respect to the termination of the Executive's employment
will be reviewed with, and be subject to comment by, the Executive prior to its
issuance or publication and that such announcement shall characterize the
Executive's termination of employment as a retirement to pursue other interests.
Except as otherwise provided in this Agreement, payment of any cash compensation
hereunder relating to the Employment Agreements shall be made within five days
of the date of this Agreement pursuant to Section 6.10 of the Employment
Agreement with the Bank.

         3.   ADDITIONAL AGREEMENTS OF THE EXECUTIVE AND THE COMPANIES.  Unless
otherwise required by a court of competent jurisdiction or pursuant to any
recognized subpoena power or as is reasonably necessary in connection with any
adversarial process between the Executive and a Company, the Executive agrees
and promises that he will not make any oral or written statements or reveal any
information to any person, company, or agency which may be

<PAGE>

                                          3

construed to be negative, disparaging or damaging to the reputation or business
of either of the Companies, its subsidiaries, directors, officers or affiliates,
or which would interfere in any way with the business relations between that
Company or any of its subsidiaries or affiliates and any of their customers or
potential customers.  Unless otherwise required by a court of competent
jurisdiction or pursuant to any recognized subpoena power or as is reasonably
necessary in connection with any adversarial process between the Executive and a
Company, the Companies agree and promise that each, respectively, will not make
any oral or written statements or reveal any information to any person, company,
or agency which may be construed to be negative, disparaging or damaging to the
reputation of the Executive.

         In addition, the Executive agrees, upon the execution of this
Agreement, to tender his resignation from the board of directors (and any
committees thereof) of the Bank, the Corporation and any subsidiary or affiliate
of the Bank or the Corporation.

         4.   AGREEMENT CONFIDENTIAL.  The Executive represents and agrees
that, unless compelled by legal process or as is reasonably necessary in
connection with any adversarial process between a Company and the Executive, he
will keep the terms of this Agreement completely confidential, and that he will
not hereafter disclose any information concerning this Agreement to anyone
except his financial, legal or tax advisor(s), his accountants, and his
immediate family; provided that these individuals agree to keep said information
confidential and not disclose it to others.

         Each Company represents and agrees that, unless compelled by legal
process or applicable legal requirements, or as is reasonably necessary in
connection with any adversarial process between the Company and the Executive,
it will keep the terms of this Agreement completely confidential, and that it
will not hereafter disclose any information concerning this Agreement to anyone
except its financial, legal or tax advisor(s), its accountants, its directors,
and those employees of the Company who have a need to know about its terms;
provided that these individuals agree to keep said information confidential and
not disclose it to others; and provided further that the Executive shall have
the opportunity to review and comment upon any proposed public disclosure
pursuant to applicable legal requirements with respect to any of the terms of
this Agreements.

         5.   NONCOMPETITION.  In consideration of the benefits to the
Executive under this Agreement and for other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged by the Executive,
the Executive shall not, during the Noncompetition Period (as hereinafter
defined), directly or indirectly, act as a director, officer, employee, manager,
trustee, agent, partner, advisor, joint venturer, representative or consultant
of, with or to, or otherwise engage in any capacity whatsoever, any commercial,
savings and loan, or thrift banking business(es) located in or doing business in
or with respect to New York State, New Jersey and/or Connecticut that actually
compete to a substantial extent with those businesses either Company and its
subsidiaries are engaged in on September 6, 1996 which competition is reasonably
likely to have a material adverse effect on the Company and its subsidiaries
taken as a

<PAGE>

                                          4

whole.  For purposes of this Section 5, the "Noncompetition Period" shall mean
the period beginning on September 6, 1996 and ending on December 31, 1996.

         6.   ADDITIONAL RESTRICTIONS.  For a period of two years from the date
of this Agreement (the "Restricted Period"), except as specifically requested in
writing by a Company, the Executive, singly or with any other person or directly
or indirectly, shall not propose, enter into, or agree to enter into, or
encourage any other person to propose, enter into, or agree to enter into (i)
any form of business combination, acquisition or other transaction relating to
the Company or (ii) any form of restructuring, recapitalization or similar
transaction with respect to the Company.

         Furthermore, during the Restricted Period, except as specifically
requested in writing by a Company, the Executive shall not, singly or with any
other person or directly or indirectly, (1) acquire, or offer, propose or agree
to acquire, by tender offer, purchase or otherwise, any voting securities of the
Company except through the exercise of Options and except for the purchase of up
to an additional 25,000 shares of voting common stock of the Corporation on the
open market, (2) make, or in any way participate in, any solicitation of proxies
or written consents with respect to voting securities of the Company (it being
understood that the mere execution of a proxy or written consent shall not be
treated as constituting participation in such a solicitation), (3) become a
participant in any election contest with respect to the Company, (4) seek to
influence any person with respect to the voting or disposition of any voting
securities of the Company, (5) demand a copy of the Company's list of
stockholders or its other books and records, (6) participate in or encourage the
formation of any partnership, syndicate or other group that owns or seeks or
offers to acquire beneficial ownership of any voting securities of the Company
or that seeks to affect control of the Company or for the purpose of
circumventing any provision of this Agreement or (7) otherwise act to seek or to
offer to control or influence, in any manner, the management, Board of Directors
or policies of the Company.

         During the period beginning on September 6, 1996 and ending on
September 6, 1997, the Executive shall not directly or indirectly (i) solicit
for employment any of the current directors, officers or managers of either
Company or (ii) induce any such directors, officers or managers to terminate his
or her employment with either Company.

         7.   RELEASES.  In consideration of the payments and benefits to the
Executive under this Agreement and for other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged by the Executive,
the Executive knowingly, voluntarily and unconditionally hereby forever waives,
releases and discharges, and covenants never to sue on, any and all claims,
liabilities, causes of actions, judgments, orders, assessments, penalties,
fines, expenses and costs (including without limitation attorneys' fees) and/or
suits of any kind arising out of any actions, events or circumstances before the
date of execution of this Agreement ("Claims") which the Executive has, ever had
or may have, or which the Executive's heirs, executors, administrators and
assigns, or any of them hereafter can, shall or may have, including, without
limitation, any Claims arising in whole or in part from the Executive's
employment or the termination of the Executive's employment with either Company
or the manner of said

<PAGE>

                                          5

termination; provided, however, that this Section 7 shall not apply to any of
the obligations of the Company specifically provided for in this Agreement.
This Agreement is intended as a full and final settlement and compromise of
each, every and all Claims of every kind and nature, whether known or unknown,
which have been or could be asserted against either Company and/or any of its
subsidiaries, shareholders, officers, directors, agents, and employees, past or
present, and their respective heirs, successors and assigns (collectively, the
"Releasees"), including, without limitation --

    (1)  any Claims arising out of any employment agreement (other than the
         Employment Agreements) or other contract (including, without
         limitation, the Employment Agreements), side-letter, resolution,
         promise or understanding of any kind, whether written or oral or
         express or implied;

    (2)  any Claims arising under the Age Discrimination in Employment Act of
         1967, as amended ("ADEA"), 29 U.S.C.  Sections  621 ET SEQ.; and

    (3)  any Claims arising under any federal, state, or local civil rights,
         human rights, anti-discrimination, labor, employment, contract or tort
         law, rule, regulation, order or decision, including, without
         limitation, the Family and Medical Leave Act, the Employee Retirement
         Income Security Act of 1974, the Americans with Disabilities Act of
         1990, 42 U.S.C. Sections 12101 ET SEQ., and Title VII of the Civil
         Rights Act of 1964, 42 U.S.C.  Sections 2000 ET SEQ., and as each of
         these laws have been or will be amended,

except that to the extent that any governmental authority or other third party,
I.E., other than one of the Releasees, files a charge or institutes an
investigation, lawsuit or any proceeding against the Executive based on any
event, occurrence or omission during the period of the Executive's employment
with a Company, in which case the Executive will be permitted to implead or
bring a court action against the Company and/or any of the Releasees for
indemnification of any liability or other appropriate remedy, provided such
impleader or court action would be available but for this Agreement.

         In consideration of the obligations of the Executive under this
Agreement and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged by the Companies, the Companies
knowingly, voluntarily and unconditionally hereby forever waive, release and
discharge, and covenant never to sue on, any and all Claims which the Companies
have, ever had or may have, including, without limitation, any Claims arising in
whole or in part from the Executive's employment or the termination of the
Executive's employment with either Company or the manner of said termination;
provided, however, that this Section 7 shall not apply to any of the obligations
of the Executive specifically provided for in this Agreement.  This Agreement is
intended  as a full and final settlement and compromise of each,

<PAGE>

                                          6

every and all Claims of every kind and nature, whether known or unknown, which
have been or could be asserted against the Executive and his respective heirs,
successors and assigns.

         Notwithstanding anything to the contrary in this Section 7, (a) the
Executive does not release (i) any claim he may have under any employee benefit
plan subject to the Employee Retirement Income Security Act of 1974, as amended,
in which he was a participant during his employment with either Company for the
payment of a benefit thereunder to which he would be entitled upon his
termination of employment on September 6, 1996 in accordance with the terms of
such plan or (ii) any claim that he may have under this Agreement, (b) the
Companies do not release any claim that either may have under this Agreement,
and (c) this Section 7 shall not apply to any of the obligations of the Company
specifically provided for in the Employment Agreements, the SIP, the MRP, and
the DPP, all as modified by this Agreement.

         The Executive understands that this Agreement affects significant
rights and represents and agrees that he has carefully read and fully
understands all of the provisions of this Agreement, that he is voluntarily
entering into this Agreement, and that he has been advised to consult with and
has in fact consulted with legal counsel before entering into this Agreement.
In particular, the Executive acknowledges that he has been given twenty-one (21)
days during which time he has carefully considered and voluntarily approved the
terms of this Agreement.  The Executive understands that, pursuant to the
provisions of the ADEA, he shall have a period of seven (7) days from the date
of execution of this Agreement during which he may revoke the release provided
under this Section 7 with respect to any claims under ADEA via hand delivery of
a notice of revocation to the offices of the Corporation.  This release shall
not become effective or enforceable with respect to any Claims under ADEA until
the revocation period described above has expired. If the Executive elects to
revoke the portion of this release with respect to Claims under ADEA as provided
above, each of the Companies shall have the right, upon written notice to the
Executive within 30 days after such revocation, to terminate all or any portion
of its obligations under this Agreement.

         This Agreement does not constitute any admission of wrongdoing, or
evidence thereof, on the part of any of the parties hereto or the Releasees.
Except as required by court order, or to enforce the terms of this Agreement,
this Agreement may not be used in any court or administrative proceeding.

         8.  ADDITIONAL PERQUISITES.  The Executive shall be entitled to
continued use of his leased company car until December 31, 1996, on the same
terms and conditions as exist on the date hereof; PROVIDED, HOWEVER, that in no
event shall the Executive be responsible for any excess mileage charges due upon
termination of the lease agreement on or about December 31, 1996.

         The Corporation shall provide the Executive (at no cost to the
Executive) with outplacement counseling and services at an outplacement firm of
the Corporation's choice, which firm shall arrange for reasonable office and
secretarial services until December 31, 1996 (as approved in advance by the
Corporation).


<PAGE>

                                          7

         The Corporation and the Bank agree to provide within a reasonable
period of time the reference letter attached hereto as "Exhibit A", addressing
the Executive's character and performance for the Bank, to be signed by the
Chief Executive Officer of the Bank on the date hereof, whenever a formal
inquiry is made of the Corporation or the Bank by an party seeking to affiliate
with the Executive or have the Executive affiliate with it.

         The Executive shall be permitted, for the purpose of removing his
personal property and effects and for the period commencing on the date of this
Agreement and ending on September 30, 1996, access to his current office space
at the Bank's principal corporate offices after 5:30 p.m. during weekdays and
between 9:00 a.m. and 9:00 p.m. on week-ends.

         The Companies confirm that the Executive is entitled to the welfare
benefit continuation provided for in the resolution of the Bank's Board of
Trustees, dated April 27, 1993.

         The Executive shall be entitled to receive an assignment or transfer
of the life insurance policy relating to the Executive under the Companies
current "split-dollar" life insurance program without consideration; PROVIDED,
HOWEVER, that the Executive shall be responsible for any premium payments due
and payable after the date of this Agreement.


         9.   SCOPE OF AGREEMENT; ENFORCEABILITY.  This Agreement constitutes
the entire understanding and agreement between the Companies and the Executive
with regard to all matters herein and supersedes all prior oral and written
agreements and understandings of the parties with respect to such matters,
whether express or implied, other than the Employment Agreements.

         This Agreement shall inure to the benefit of and be enforceable by the
Executive's heirs, beneficiaries and/or legal representatives.  This Agreement
shall inure to the benefit of and be binding upon the Companies and their
respective successors and assigns.

         If any term or provision of this Agreement, or the application thereof
to any person or circumstances, will to any extent be invalid or unenforceable,
the remainder of this Agreement, or the application of such terms to persons or
circumstances other than those as to which it is invalid or unenforceable, will
not be affected thereby, and each term of this Agreement will be valid and
enforceable to the fullest extent permitted by law.

         10.  AMENDMENTS/WAIVER.  This Agreement may not be amended, waived, or
modified otherwise than by a written agreement executed by the parties to this
Agreement or their respective successors and legal representatives.  No waiver
by any party to this Agreement of any breach of any term, provision or condition
of this Agreement by the other party shall be deemed a waiver of a similar or
dissimilar condition or provision at the same time, or any prior or subsequent
time.

<PAGE>

                                          8

         11.  NOTICES.  All notices and other communications hereunder shall be
in writing and shall be deemed given when received by hand-delivery to the other
party, by facsimile transmission, by overnight courier, or by registered or
certified mail, return receipt requested, postage prepaid, addressed as follows:

         If to the Executive:     Mr. William E. Viklund
                                  110 Grist Mill Lane
                                  Plandome Manor, New York 11030


         with a copy to:          Gerald P. Wolf, Esq.
                                  Meltzer, Lippe, Goldstein, Wolf
                                    & Schlissel, P.C.
                                  190 Willis Avenue
                                  Mineola, New York 11501

         If to the Corporation:   Long Island Bancorp, Inc.
                                  201 Old Country Road
                                  Melville, New York 11747
                                  Attn: Corporate Secretary

         with a copy to:          Mel M. Immergut, Esq.
                                  Milbank, Tweed, Hadley & McCloy
                                  1 Chase Manhattan Plaza
                                  New York, New York 10005

or to such other address as either party shall have furnished to the other in
writing in accordance herewith.  Notices and communications shall be effective
when actually received by the addressee.

         12.  NEW YORK LAW.    This Agreement shall be construed and enforced
in accordance with the laws of the State of New York without reference to its
choice of law provisions and shall be binding upon the parties and their
respective heirs, executors, successors and assigns.

         13.  COUNTERPARTS.  This Agreement may be executed in several
counterparts, each of which shall be deemed to be an original, but all of which
together shall constitute one and the same instrument.

         IN WITNESS WHEREOF, the Companies and the Executive have caused this
Agreement to be executed as of the date first above written.


                                       LONG ISLAND BANCORP, INC.


                                       By:__________________________

<PAGE>

                                          9

                                           Name:
                                           Title:


                                       LONG ISLAND SAVINGS BANK, FSB


                                       By:__________________________
                                           Name:
                                           Title:


                                       _____________________________
                                           William E. Viklund