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                                                                   EXHIBIT 10.42

                              EMPLOYMENT AGREEMENT

         EMPLOYMENT AGREEMENT, dated as of September 28, 2000, between OSI
PHARMACEUTICALS, INC., a Delaware corporation having a place of business at 106
Charles Lindbergh Blvd., Uniondale, NY 11553 (the "Company"), and Nicholas G.
Bacopoulos, Ph.D., who resides at 39 Church Street, Stonington, CT 06378
("Executive").

                                   WITNESSETH:

         WHEREAS, the Company desires to engage Executive to perform services
for the Company and any subsidiary or affiliate of the Company, and Executive
desires to perform such services, on the terms and conditions hereinafter set
forth;

         NOW, THEREFORE, the Company and Executive, in consideration of the
mutual promises contained herein and other good and valuable consideration, the
receipt, adequacy and sufficiency of which are hereby acknowledged, hereby agree
as follows:

         1. Term. The Company hereby employs Executive, and Executive hereby
accepts such employment, upon the terms and conditions hereinafter set forth.
Executive shall perform the duties required of him hereunder during the period
commencing on September 28, 2000 and ending on September 28, 2003; provided,
however, that on September 28, 2003, and on each September 28 thereafter, such
period shall be automatically extended by one additional year unless at least 60
days prior to any such September 28 either party shall deliver to the other
written notice that such period will not be extended, in which case this
Agreement will terminate upon the expiration of this then existing term of this
Agreement, including any previous extension. The period during which Executive
shall perform the services required of him hereunder (as same may be extended as
provided in this Paragraph 1 or reduced as hereinafter provided) is hereinafter
referred to as the "Employment Period."

         2. Duties.

                  (a)      Executive shall serve, at the pleasure of the Board
                           of Directors of the Company, as President and Head of
                           Research and Development of the Company. In his
                           capacities as President and Head of Research and
                           Development, the Executive shall report to Colin
                           Goddard, Ph.D., the Chief Executive Officer of the
                           Company, and perform for the Company, and any
                           subsidiary or affiliate of the Company, such duties
                           generally associated with such positions as well as
                           such other duties consistent with such positions as
                           may be prescribed from time to time by the Board of
                           Directors.

                  (b)      Executive agrees to devote his full time, labor,
                           energies and attention to the performance of his
                           duties hereunder, subject to the provisions of
                           Paragraph 10(a) hereof.

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                  (c)      Executive agrees not to become involved in any
                           personal investment or business matters which may
                           detract from the performance of his duties or
                           otherwise adversely affect the Company or any
                           subsidiary or affiliate of the Company.

         3. Place of Performance. In connection with his employment by the
Company, Executive shall be based at the principal executive offices of the
Company, but shall be available to travel at such times and to such places as
may be reasonably necessary in connection with the performance of his duties
hereunder.

         4. Compensation and Payments.

                  (a)      Base Salary. During the Employment Period, Executive
                           shall receive a minimum base salary at the annual
                           rate of $300,000, plus such other amounts, if any, as
                           the Board of Directors of the Company, in its sole
                           discretion, may from time to time determine, less all
                           applicable estimated and/or actual withholding and
                           employment-related taxes. Executive's base salary
                           shall be reviewed annually, provided, however, that
                           in no event shall Executive's base salary be reduced
                           below an annual rate of $300,000. Executive's salary
                           shall be payable in bi-weekly installments or at such
                           other frequency as the Company may from time to time
                           determine.

                  (b)      Signing Bonus. The Executive shall receive a $75,000
                           bonus, payable in one lump sum payment, less all
                           applicable estimated and/or actual withholding and
                           employment-related taxes, upon the execution of this
                           Agreement by the Company and Executive.

                  (c)      Incentive Bonus Opportunity. In addition to the
                           compensation set forth in Paragraphs 4(a) and (b),
                           Executive may receive incentive bonus compensation in
                           respect of each fiscal year ending during the
                           Employment Period (the "Annual Award"). The amount,
                           if any, of each such Annual Award shall be determined
                           by the Board of Directors of the Company in its sole
                           discretion. Executive shall not receive any Annual
                           Award unless he is employed by the Company at the end
                           of the fiscal year to which such Annual Award
                           relates. Any Annual Award will be paid to Executive
                           within 120 days following the end of the fiscal year
                           to which such Annual Award relates.

                  (d)      Relocation Payment. Executive shall receive a
                           relocation payment of $200,000, less all applicable
                           estimated and/or actual withholding and
                           employment-related taxes.

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         5. Stock Options.

                  (a)      The Executive shall receive a stock option to
                           purchase 100,000 shares of the Company's Common
                           Stock, par value $.0l per share ("Common Stock"),
                           with an exercise price of $22.56 per share. The stock
                           option granted under this Paragraph shall be granted
                           pursuant to the Company's 1999 Incentive and
                           Non-Qualified Stock Option Plan (the "Plan") and a
                           Stock Option Agreement between the Company and the
                           Executive dated as of the date hereof (collectively,
                           with the Stock Option Agreement referred to in
                           Paragraph 5(b), the "Option Agreements"). All options
                           granted under this Paragraph shall vest on the date
                           hereof.

                  (b)      The Executive shall also receive a stock option to
                           purchase 150,000 shares of Common Stock with an
                           exercise price of $45.13 per share. The stock option
                           granted under this Paragraph shall be granted
                           pursuant to the plan and a Stock Option Agreement
                           between the Company and the Executive dated as of the
                           date hereof. All options granted under this Paragraph
                           shall vest over three years.

                  (c)      Executive shall be eligible to receive additional
                           stock options as the Board of Directors of the
                           Company shall determine in its sole discretion and in
                           accord with established Company policy and incentive
                           goals.

         6. Expenses. During the Employment Period, Executive shall be entitled
to reimbursement for all reasonable out-of-pocket expenses necessarily incurred
in performing services hereunder within the limits of authority which may be
established from time to time by the Board of Directors, provided that Executive
properly accounts for such expenses in accordance with Company policy.

         7. Employee Benefits.

                  (a)      Use of Automobile. The Company shall provide
                           Executive with the use of an automobile during the
                           Employment Period and shall reimburse Executive for
                           his reasonable and necessary expenses in connection
                           with the use of such vehicle in furtherance of the
                           business of the Company, provided that Executive
                           properly accounts for such expenses in accordance
                           with Company policy.

                  (b)      Vacation. Executive shall be entitled to one month
                           paid vacation per calendar year which may be taken at
                           such time or times as Executive may elect, subject to
                           the needs of the Company's business. Executive shall
                           also be entitled to all paid holidays given by the
                           Company to its senior executive officers.

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                  (c)      Other Benefits. Executive shall be entitled to
                           participate in such term life insurance, basic
                           medical, major medical, dental, hospitalization
                           coverage (which may be extended to cover dependents
                           at extra charge to the Executive), 401(k) savings and
                           investment plan, tuition reimbursement plan, and
                           other employee benefit plans established by the
                           Company from time to time and generally made
                           available to employees at levels similar to
                           Executive's for which he meets the eligibility
                           requirements.

         8. Termination.

                  (a)      The Company may terminate this Agreement at any time
                           after the first anniversary of the date of
                           commencement of the Employment Period, and for any
                           reason whatsoever (or for no reason), by giving not
                           less than 30 days' prior written notice to Executive.
                           In the event this Agreement is terminated by the
                           Company other than for a reason set forth in
                           Paragraph 8(b) hereof, (i) Executive shall be
                           entitled to receive his base salary at the rate in
                           effect on the date notice of termination is given
                           through the effective date of such termination and
                           any Annual Award granted through such date which has
                           not yet been paid; and (ii) Executive shall continue
                           to receive his base salary at the rate in effect on
                           the date notice of termination is given for the
                           twelve months immediately succeeding the effective
                           date of such termination.

                  (b)      Notwithstanding anything herein contained to the
                           contrary, if after the date hereof and prior to the
                           end of the Employment Period, (i) either (A)
                           Executive shall be physically or mentally
                           incapacitated or disabled or otherwise unable fully
                           to discharge his duties hereunder ("Disabled") for a
                           period of 90 consecutive days or for an aggregate of
                           90 days within any period of twelve consecutive
                           months, (B) Executive shall be convicted of a felony
                           or other crime involving moral turpitude, (C)
                           Executive shall commit any act or omit to take any
                           action in bad faith and to the detriment of the
                           Company or any subsidiary or affiliate of the
                           Company, or (D) Executive shall breach any material
                           term of this Agreement and fail to correct such
                           breach within 10 days after receiving notice of the
                           same, then, and in each such case, the Company shall
                           have the right to give notice of termination of
                           Executive's services hereunder as of a date to be
                           specified in such notice (which date may be the date
                           such notice is given), and this Agreement shall
                           terminate on the date so specified; or (ii) Executive
                           shall die, then this Agreement shall terminate the
                           date of Executive's death. If this Agreement is
                           terminated by the Company for any of the reasons set
                           forth in this Paragraph 8(b), Executive or his
                           estate, as the case may be, shall be entitled to
                           receive his base salary at the rate in effect on the
                           date notice of termination is given or the date of
                           Executive's death, as the case may be, to the date on

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                           which termination shall take effect and any Annual
                           Award granted through such date which has not been
                           paid; provided, however that if Executive is
                           Disabled; the amount payable to Executive pursuant to
                           this Paragraph 8(b) shall be reduced by an amount
                           equal to the amounts, if any, to which he is entitled
                           with respect to such period pursuant to any insurance
                           or other plan established by the Company in which he
                           is a participant.

                  (c)      Termination by the Employee. The Executive may
                           terminate this agreement after the date herein if in
                           the event of a change of control of the Company or
                           for any other reason his title, responsibilities or
                           salary are reduced from those in effect at the time
                           and he shall be entitled to full payment for the
                           remaining term of this Agreement. However, the
                           payment shall not be less than nine months pay in any
                           event. Upon such termination, all outstanding stock
                           options granted to the Executive shall become fully
                           vested.

         9. Confidentiality.

                  (a)      Executive shall continue to treat as confidential any
                           proprietary, confidential or secret information
                           relating to the business or interests of the Company
                           or any subsidiary or affiliate of the Company,
                           including, without limitation, the organizational
                           structure, operations, business plans or technical
                           projects of the Company or any subsidiary or
                           affiliate of the Company, and any research datum or
                           result, invention, trade secret, customer list,
                           process or other work product developed by or for the
                           Company or any subsidiary or affiliate of the
                           Company, whether on the premises of the Company or
                           elsewhere ("Confidential Information"). Beginning on
                           the date hereof, and at any time hereafter, Executive
                           shall not disclose, utilize or make accessible in any
                           manner or in any form any Confidential Information
                           other than in connection with performing the services
                           required of him under this Agreement, without the
                           prior written consent of the Company. Notwithstanding
                           the foregoing, the provisions of this Paragraph 9(a)
                           shall not apply to any proprietary, confidential or
                           secret information or other research datum or result,
                           invention, trade secret, customer list or work
                           product which is, at the commencement of this
                           Agreement or at some later date, publicly known under
                           circumstances involving no breach of this Agreement
                           or is lawfully and in good faith made available to
                           Executive by a third party under no obligation of
                           confidentiality with respect thereto.

                  (b)      Executive hereby agrees that any and all information,
                           inventions and discoveries, whether or not
                           patentable, that he conceives and/or creates during
                           the Employment Period and any extensions thereof, and
                           which are a direct or indirect result of work
                           performed hereunder, shall be the

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                           sole and exclusive property of the Company. Executive
                           hereby assigns to the Company any and all right,
                           title and interest which he has or may acquire in the
                           same. Executive further agrees that he will promptly
                           execute any and all applications, assignments or
                           other instruments which an officer of the Company or
                           the Board of Directors of the Company shall deem
                           necessary or useful in order to apply for and obtain
                           Letters Patent in the United States and all foreign
                           countries for said information, inventions and
                           discoveries and in order to assign and convey to the
                           Company the sole and exclusive right, title and
                           interest in and to said information, inventions,
                           discoveries, patent applications and patents thereon.
                           The Company will bear the cost of preparation of all
                           such patent applications and assignments, and the
                           cost of prosecution of all such patent applications
                           in the United States Patent Office and in the patent
                           offices of foreign countries.

                  (c)      All documents, records, apparatus, equipment and
                           other physical property furnished to Executive by the
                           Company or produced by Executive or others in
                           connection with his employment shall be and remain
                           the sole property of the Company. Executive will
                           return and deliver such property to the Company as
                           and when requested by the Company.

                  (d)      Executive agrees that the provisions of this
                           Paragraph 9 shall survive the termination of his
                           employment and of this Agreement.

         10. Non-Competition.

                  (a)      Executive agrees that, during the period he is
                           employed by the Company or any subsidiary or
                           affiliate of the Company, under this Agreement or
                           otherwise, he will not engage in, or otherwise
                           directly or indirectly be employed by, or act as a
                           consultant, advisor or lender to, or be a director,
                           officer, employee, stockholder, owner or partner of
                           any other business or organization, whether or not
                           such business or organization now is or shall then be
                           competing with the Company or any parent, subsidiary
                           or affiliate of the Company; provided, however, that
                           Executive shall not be prohibited either from
                           managing his own personal investments on his own
                           personal time or from serving on up to three outside
                           boards of directors or advisory boards, so long as
                           such activities do not (i) involve a business or
                           organization which competes with the Company or any
                           subsidiary or affiliate of the Company, (ii)
                           interfere or conflict with the performance of his
                           duties as an employee of the Company or any
                           subsidiary or affiliate of the Company, (iii)
                           otherwise result in, a breach of any of the
                           provisions of this Agreement, or (iv) in the case of
                           serving as a director or advisory board member of
                           other companies, such activities, for all such
                           companies do not require, in the

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                           aggregate, more than 15 days per year, including
                           travel time. Executive further agrees that (y) if his
                           employment with the Company is terminated by the
                           Company pursuant to Paragraphs 8(a) or 8(b)(i)
                           hereof, or (z) if he resigns or otherwise fails or
                           refuses to perform the services required of him under
                           this Agreement other than as a result of-a breach of
                           this Agreement by the Company (which breach is not
                           cured within 30 days after receiving notice thereof),
                           then during the two-year period commencing on the
                           date he ceases to be employed by any of the Company
                           or any subsidiary or affiliate of the Company, under
                           this Agreement or otherwise, Executive shall not
                           directly or indirectly compete with or be engaged in
                           the same business as the Company or any subsidiary or
                           affiliate of the Company, or be employed by, or act
                           as consultant, advisor or lender to, or be a
                           director, officer, employee, stockholder, owner or
                           partner of, any business or organization which, at
                           the time of such cessation, directly or indirectly
                           competes with or is engaged in the same business as
                           the Company or any subsidiary or affiliate of the
                           Company; provided, however, that if Executive's
                           employment with the Company is terminated pursuant to
                           Paragraphs 8(a) or 8(b)(i)(A) hereof, Executive's
                           obligations pursuant to this sentence shall continue
                           only so long as the Company pays Executive
                           compensation at the same rate compensation was being
                           paid to him pursuant to Paragraph 4 of this Agreement
                           at the time of such termination (subject, in the case
                           of termination pursuant to Paragraphs 8(a).
                           Notwithstanding anything contained herein to the
                           contrary, the provisions of this Paragraph 10(a) will
                           not be deemed breached merely because Executive owns
                           not more than 1% of the outstanding common stock of a
                           corporation if, at the time of its acquisition by
                           Executive, such stock is listed on a national
                           securities exchange, is reported on NASDAQ, or is
                           regularly traded in the over-the-counter market by a
                           member of a national securities exchange.

                  (b)      Executive agrees that for a period of three years
                           from the termination of this Agreement he will not,
                           directly or indirectly, employ or solicit the
                           employment or engagement by others of any employees
                           of, or consultants hired by, the Company, or any
                           subsidiary or affiliate of the Company, without the
                           prior written consent of the Company.

                  (c)      The obligations of Executive pursuant to this
                           Paragraph 10 shall survive the termination of this
                           Agreement.

         11. Equitable Relief. Executive acknowledges that the restrictions
contained in Paragraphs 9 and 10 of this Agreement are reasonable in view of the
nature of the business in which the Company is engaged and the knowledge he will
obtain concerning the Company's business (and the business of any subsidiary or
affiliate of the Company), and that any breach of his obligations under
Paragraphs 9 and 10 hereof will cause the Company irreparable harm

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for which the Company will have no adequate remedy at law. As a result, the
Company shall be entitled to the issuance by a court of competent jurisdiction
of an injunction, restraining order or other equitable relief in favor of itself
restraining Executive from committing or continuing any such violation, and
Executive consents to such an injunction, restraining order or other equitable
relief. Any right to obtain an injunction, restraining order or other equitable
relief hereunder will not be deemed a waiver of any right to assert any other
remedy the Company may have under this Agreement or otherwise at law or in
equity.

         12. Representations and Warranties. Executive represents and warrants
to the Company that (i) Executive is under no contractual or other restriction
or obligation which is inconsistent with the execution of this Agreement, the
performance of his duties hereunder or the other rights of the Company and any
subsidiary or affiliate of the Company hereunder, and (ii) Executive is under no
physical or mental disability that would hinder the performance by him of his
duties under this Agreement.

         13. Assignment. Under no circumstances shall Executive assign, pledge
or otherwise dispose of any of his rights or obligations under this Agreement,
and any such attempted assignment, pledge or disposition shall be void and
shall, at the Company's option, relieve the Company of all its obligations under
this Agreement. The Company may assign any of its rights or obligations under
this Agreement to any parent, subsidiary, affiliate or successor.

         14. Entire Agreement. This Agreement, the Option Agreements and the
Plan represent the entire agreement between the Company and Executive with
respect to the subject matter hereof and there have been no oral or other
agreements of any kind whatsoever as a condition precedent or inducement to the
signing of this Agreement or otherwise concerning this Agreement or the subject
matter hereof.

         15. Waivers. Any waiver of any breach of any terms or conditions of
this Agreement shall not operate as a waiver of any other breach of such terms
or conditions or any other term or condition, nor shall any failure to enforce
any provision hereof on any one occasion operate as a waiver of such provision
or of any other provision hereof or a waiver of the right to enforce such
provision or any other provision on any subsequent occasion.

         16. Amendments. This Agreement may not be amended, nor shall any
waiver, change, modification, consent or discharge be effected, except by an
instrument in writing executed by or on behalf of the party against whom
enforcement of any such amendment, waiver, change, modification, consent or
discharge is sought.

         17. Severability.

                  (a)      If any provision of this Agreement shall be held or
                           deemed to be invalid, inoperative or unenforceable as
                           written, it shall be construed, to the greatest
                           extent possible, in a manner which shall render it
                           valid and enforceable and any limitation on the scope
                           or duration of any such

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                           provision necessary to make it valid and enforceable
                           shall be deemed to be part thereof.

                  (b)      If any provision of this Agreement shall be held or
                           deemed to be invalid, inoperative or unenforceable as
                           applied to any particular case in any jurisdiction or
                           jurisdictions, or in all jurisdictions or in all
                           cases, because of the conflict or any provision with
                           any constitution or statute or rule of public policy
                           or for any other reason, such circumstance shall not
                           have the effect of rendering the provision or
                           provisions in question invalid, inoperative or
                           unenforceable in any other jurisdiction or in any
                           other case or circumstance or of rendering any other
                           provision or provisions herein contained invalid,
                           inoperative or unenforceable to the extent that such
                           other provisions are not themselves actually in
                           conflict with such constitution, statute or rule of
                           public policy, but this Agreement shall be reformed
                           and construed in any such jurisdiction or case as if
                           such invalid, inoperative or unenforceable provision
                           had never been contained herein, and such provision
                           reformed so that it would be valid, operative arid
                           enforceable to the maximum extent permitted in such
                           jurisdiction or in such case.

         18. Governing Law. This Agreement shall be governed by and construed
and enforced in accordance with the laws of the State of New York without giving
effect to rules governing conflict of laws.

         19. Courts. Any action to enforce any of the provisions of this
Agreement may be brought in the courts of the State of New York. The parties
hereby consent to the jurisdiction of the courts of the State of New York.

         20. Notices. Any notice or other communication required or permitted by
this Agreement shall be in writing and personally delivered or mailed by
certified mail, return receipt requested, addressed to the parties at their
addresses set forth above, or to such other addresses as one party may specify
to the other party, from time to time, in writing. Any notice or other
communication given by certified mail shall be deemed given at the time of
certification thereof, except for a notice changing a party's address which
shall be deemed given at the time of receipt thereof.

         21. Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed to be an original but all of which
together will constitute one and the same instrument.

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         IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date and year first above written.

                                      OSI PHARMACEUTICALS, INC.


                                      By:      /s/ COLIN GODDARD
                                         --------------------------------
                                      Name:    Colin Goddard, Ph.D.
                                      Title:   Chairman and CEO

                                      EXECUTIVE


                                               /s/ NICHOLAS G. BACOPOULOS
                                         --------------------------------
                                               Nicholas G. Bacopoulos, Ph.D.


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