Document:

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                                                                     Exhibit 4.3

                        THE SANTA CRUZ OPERATION, INC.
                         EMPLOYEE STOCK PURCHASE PLAN
                          (As Amended November 1999)

The following constitute the provisions of the Employee Stock Purchase Plan of
The Santa Cruz Operation, Inc.

1.   Purpose.
     -------

     The purpose of the Plan is to provide employees of the Company and its
     Designated Subsidiaries with an opportunity to purchase Common Stock of the
     Company through accumulated payroll deductions. It is the intention of the
     company to have the Plan qualify as an "Employee Stock Purchase Plan" under
     Section 423 of the Internal Revenue Code of 1986, as amended. The
     provisions of the Plan, accordingly, shall be construed so as to extend and
     limit participation in a manner consistent with the requirements of that
     section of the Code.

2.   Definitions.
     -----------

     a)   "Board" shall mean the Board of Directors of the company.
           -----

     b)   "Code" shall mean the Internal Revenue Code of 1986, as amended.
           ----

     c)   "Common Stock" shall mean the Common Stock of the Company.
           ------------

     d)   "Company" shall mean The Santa Cruz Operation, Inc., a California
           -------
          corporation.

     e)   "Compensation" shall include all base pay, overtime pay, bonus and
           ------------
          commissions and shall exclude all other amounts.

     f)   "Designated Subsidiaries" shall mean the Subsidiaries which have been
           -----------------------
          designated by the Board from time to time in its sole discretion as
          eligible to participate in the Plan.

     g)   "Employee" shall mean any individual who is a regular employee of the
           --------
          Company for purposes of tax withholding under the Code whose customary
          employment with the Company or any Designated Subsidiary regardless of
          the number of hours worked. For purposes of the Plan, the employment
          relationship shall be treated as continuing intact while the
          individual is on sick leave or other leave of absence approved by the
          Company. Where the period of leave exceeds ninety (90) days and the
          individual's right to employment is not guaranteed either by statute
          or by contract, the employment relationship will be deemed to have
          terminated on the 91st day of such leave.

     h)   "Enrollment Date" shall mean the first day of each Offering Period.
           ---------------

     i)   "Exercise Date" shall mean the last day of each Offering Period.
           -------------

     j)   "Fair Market Value" shall mean, as of any date, the value of Common
           -----------------
          Stock determined as follows:

          i)   If the Common Stock is listed on any established stock exchange
               or a national market system, including without limitation the
               National Market System of the National Association of Securities
               Dealers, Inc. Automated Quotation ("NASDAQ") System, its Fair
               Market Value shall be the closing sale price for the Common Stock
               (or the mean of the closing bid and asked prices, if no sales
               were reported), as quoted on such exchange (or the exchange with
               the greatest volume of trading in Common Stock) or system on the
               date of such determination, as reported in The Wall Street
               Journal or such other source as the Board deems reliable, or;

          ii)  If the Common Stock is quoted on the NASDAQ system (but not on
               the National Market System thereof) or is regularly quoted by a
               recognized securities dealer but selling prices are not reported,
               its Fair Market Value shall be the mean of the closing bid and
               asked prices for the Common Stock on the date of such
               determination, as reported in The Wall Street Journal or such
               other source as the Board deems reliable, or;

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          iii)  In the absence of an established market for the Common Stock,
                the Fair Market Value thereof shall be determined in good faith
                by the Board.

          iv)   For purposes of the Enrollment Date under the first Offering
                Period under the Plan, the Fair Market Value of the Common Stock
                shall be the Price to Public as set forth in the final
                prospectus filed with the Securities and Exchange commission
                pursuant to Rule 424 under the Securities Act of 1933, as
                amended.

     k)   "Offering Period" shall mean a period of approximately six (6) months,
           ---------------
          commencing on the first Trading Day on or after February 1 and
          terminating on the last Trading Day in the period ending the following
          July 31, or commencing on the first Trading Day on or after August 1
          and terminating on the last Trading Day in the period ending the
          following January 31, during which an option granted pursuant to the
          Plan may be exercised. The duration, commencement and termination of
          Offering Periods may be changed pursuant to Section 4 of this Plan.

     l)   "Purchase Price" shall mean an amount equal to 85% of the Fair Market
           --------------
           Value of a share of Common Stock on the Enrollment Date or on the
           Exercise Date, whichever is lower.

     m)   "Reserves" shall mean the number of shares of Common Stock covered by
           --------
          each option under the Plan which have not yet been exercised and the
          number of shares of Common Stock which have been authorized for
          issuance under the Plan but not yet placed under option.

     n)   "Subsidiary" shall mean a corporation, domestic or foreign, of which
           ----------
          not less than 50% of the voting shares are held by the Company or a
          Subsidiary, whether or not such corporation now exists or is hereafter
          organized or acquired by the Company or a Subsidiary.

     o)   "Trading Day" shall mean a day on which national stock exchanges and
           -----------
          the National Association of Securities Dealers Automated Quotation
          (NASDAQ) System are open for trading.

3.   Eligibility.
     -----------

     a)   Any Employee (as defined in Section 2(g)), who shall be employed by
          the Company on a given Enrollment Date shall be eligible to
          participate in the Plan.

     b)   Any provisions of the Plan to the contrary notwithstanding, no
          Employee shall be granted an option under the Plan

          i)  to the extent, immediately after the grant, such Employee (or any
              other person whose stock would be attributed to such Employee
              pursuant to Section 424(d) of the Code) would own capital stock of
              the Company and/or hold outstanding options to purchase such stock
              possessing five percent (5%) or more of the total combined voting
              power or value of all classes of the capital stock of the Company
              or of any Subsidiary, or

          ii) to the extent his or her rights to purchase stock under all
              employee stock purchase plans of the Company and its subsidiaries
              to accrue at a rate which exceeds Twenty-Five Thousand Dollars
              ($25,000) worth of stock (determined at the fair market value of
              the shares at the time such option is granted) for each calendar
              year in which such option is outstanding at any time.

4.   Offering Periods.
     -----------------

     The Plan shall be implemented by consecutive Offering Periods with a new
     Offering Period commencing on the first Trading Day on or after February 1
     and August 1 each year, or on such other date as the Board shall determine,
     and continuing thereafter until terminated in accordance with Section 19
     hereof. The Board shall have the power to change the duration, commencement
     and termination of Offering Periods with respect to future offerings
     without shareholder approval if such change is announced at least five (5)
     days prior to the scheduled beginning of the first Offering Period to be
     affected thereafter.

5.   Participation.
     -------------

     a)  An eligible Employee may become a participant in the Plan by completing
         a subscription agreement authorizing payroll deductions in the form of
         Exhibit A to this Plan and filing it with the Company's payroll office
         at least ten business days prior to the applicable Enrollment Date,
         however, a later date, prior to the applicable Enrollment Date may be
         established for all eligible Employees to enroll in a given Offering
         Period.

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     b)  Payroll deductions for a participant shall commence on the first
         payroll following the enrollment Date and shall end on the last payroll
         in the Offering Period to which such authorization is applicable,
         unless sooner terminated by the participant as provided in Section 10
         hereof.

6.   Payroll Deductions.
     ------------------

     a)  At the time a participant files his or her subscription agreement, he
         or she shall elect to have payroll deductions made on each pay day
         during the Offering Period in an amount of at least one percent (1%)
         and not exceeding ten percent (10%) of the Compensation which he or she
         receives on each pay day during the Offering Period, and the aggregate
         of such payroll deductions during the Offering Period shall not exceed
         ten percent (10%) of the participant's Compensation during said
         Offering Period.

     b)  All payroll deductions made for a participant shall be credited to his
         or her account under the Plan and will be withheld in whole percentages
         only. A participant may not make any additional payments into such
         account.

     c)  A participant may discontinue his or her participation in the Plan as
         provided in Section 10 hereof, or may increase or decrease the rate of
         his or her payroll deductions during the Offering Period by completing
         or filing with the Company a new subscription agreement authorizing a
         change in payroll deduction rate. The Board may, in its discretion,
         limit the number of participation rate changes during any Offering
         Period. The change in rate shall be effective with the first full
         payroll period following five (5) business days after the Company's
         receipt of the new subscription agreement unless the Company elects to
         process a given change in participation more quickly. A participant's
         subscription agreement shall remain in effect for successive Offering
         Periods unless terminated as provided in Section 10 hereof.

     d)  Notwithstanding the foregoing, to the extent necessary to comply with
         Section 423(b)(8) of the Code and Section 3(b) hereof, a participant's
         payroll deductions may be decreased to 0% at such time during any
         Offering Period which is scheduled to end during the current calendar
         year (the "Current Offering Period") that the aggregate of all payroll
         deductions which were previously used to purchase stock under the Plan
         in a prior Offering Period which ended during that calendar year plus
         all payroll deductions accumulated with respect to the Current Offering
         Period equal $21,250. Payroll deductions shall recommence at the rate
         provided in such participant' s subscription agreement at the beginning
         of the first Offering Period which is scheduled to end in the following
         calendar year, unless terminated by the participant as provided in
         Section 10 hereof.

     e)  At the time the option is exercised, in whole or in part, or at the
         time some or all of the Company's Common Stock issued under the Plan is
         disposed of, the participant must make adequate provision for the
         Company's federal, state, or other tax withholding obligations, if any,
         which arise upon the exercise of the option or the disposition of the
         Common Stock. At any time, the Company may, but will not be obligated
         to, withhold from the participant's compensation the amount necessary
         for the Company to meet applicable withholding obligations, including
         any withholding required to make available to the Company any tax
         deductions or benefits attributable to sale or early disposition of
         Common Stock by the Employee.

7.   Grant of Option.
     ---------------

     On the Enrollment Date of each Offering Period, each eligible Employee
     participating in such Offering Period shall be granted an option to
     purchase on the Exercise Date of such Offering Period (at the applicable
     Purchase Price) up to a number of shares of the Company's Common Stock
     determined by dividing such Employee's payroll deductions accumulated prior
     to such Exercise Date and retained in the Participant's account as of the
     Exercise Date by the applicable Purchase Price; provided that in no event
     shall an Employee be permitted to purchase during each Offering Period more
     than a number of Shares determined by dividing $12,500 by the Fair Market
     Value of a share of the Company's Common Stock on the Enrollment Date (the
     "Number"), except that for purposes of the first Offering period under the
     Plan, the Number shall be calculated by dividing $25,000 by the Fair Market
     Value of a share of the Company's Common Stock on the Enrollment Date, and
     provided further that all such purchases shall be subject to the
     limitations set forth in Sections 3(b) and 12 hereof. Exercise of the
     option shall occur as provided in Section 8 hereof, unless the participant
     has withdrawn pursuant to Section 10 hereof, and shall expire on the last
     day of the Offering Period.

8.   Exercise of Option.
     ------------------

     Unless a participant withdraws from the Plan as provided in Section 10
     hereof, his or her option for the purchase of shares will be exercised
     automatically on the Exercise Date, and the maximum number of full shares
     subject to option shall be purchased for

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     such participant at the applicable Purchase Price with the accumulated
     payroll deductions in his or her account. No fractional shares will be
     purchased; any payroll deductions accumulated in a participant's account
     which are not sufficient to purchase a full share shall be retained in the
     participant' s account for the subsequent Offering Period, subject to
     earlier withdrawal by the participant as provided in Section 10 hereof. Any
     other moneys left over in a participant's account after the Exercise Date
     shall be returned to the participant. During a participant's lifetime, a
     participant's option to purchase shares hereunder is exercisable only by
     him or her.

9.   Delivery.
     --------

     As promptly as practicable after each Exercise Date on which a purchase of
     shares occurs, the Company shall arrange the delivery to each participant,
     as appropriate, of a certificate representing the shares purchased upon
     exercise of his or her option.

10.  Withdrawal; Termination of Employment.
     -------------------------------------

     a)   A participant may withdraw all but not less than all the payroll
          deductions credited to his or her account and not yet used to exercise
          his or her option under the Plan at any time by giving written notice
          to the Company in the form of Exhibit B to this Plan. All of the
          participant's payroll deductions credited to his or her account will
          be paid to such participant promptly after receipt of notice of
          withdrawal and such participant's option for the Offering Period will
          be automatically terminated, and no further payroll deductions for the
          purchase of shares will be made during the Offering Period. If a
          participant withdraws from an Offering Period, payroll deductions will
          not resume at the beginning of the succeeding Offering Period unless
          the participant delivers to the Company a new subscription agreement.

     b)   Upon a participant's ceasing to be an Employee (as defined in Section
          2(g) hereof), for any reason he or she will be deemed to have elected
          to withdraw from the Plan and the payroll deductions credited to such
          participant' s account during the Offering Period but not yet used to
          exercise the option will be returned to such participant or, in the
          case of his or her death, to the person or persons entitled thereto
          under Section 14 hereof, and such participant's option will be
          automatically terminated.

     c)   A participant's withdrawal from an Offering Period will not have any
          effect upon his or her eligibility to participate in any similar plan
          which may hereafter be adopted by the Company or in succeeding
          Offering Periods which commence after the termination of the Offering
          Period from which the participant withdraws.

11.  Interest.
     --------

     No interest shall accrue on the payroll deductions of a participant in the
     Plan.

12.  Stock.
     -----

     a)   The maximum number of shares of the Company's Common Stock which shall
          be made available for sale under the Plan shall be 4,750,000 shares,
          subject to adjustment upon changes in capitalization of the Company as
          provided in Section 18 hereof. If on a given Exercise Date the number
          of shares with respect to which options are to be exercised exceeds
          the number of shares then available under the Plan, the Company shall
          make a pro rata allocation of the shares remaining available for
          purchase in as uniform a manner as shall be practicable and as it
          shall determine to be equitable.

     b)   The participant will have no interest or voting right in shares
          covered by his option until such option has been exercised.

     c)   Shares to be delivered to a participant under the Plan will be
          registered in the name of the participant or in the name of the
          participant and his or her spouse.

13.  Administration.
     --------------

     a)   Administrative Body. The Plan shall be administered by the Board or a
          committee of members of the Board appointed by the Board. The Board or
          its committee shall have full and exclusive discretionary authority to
          construe, interpret and apply the terms of the Plan, to determine
          eligibility and to adjudicate all disputed claims filed under the
          Plan. Every finding, decision and determination made by the Board or
          its committee shall, to the full extent permitted by law, be final and
          binding upon all parties.

     b)   Members of the Board who are eligible Employees are permitted to
          participate in the Plan, provided that:

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          i)   Members of the Board who are eligible to participate in the Plan
               may not vote on any matter affecting the administration of the
               Plan or the grant of any option pursuant to the Plan.

          ii)  If a Committee is established to administer the Plan, no member
               of the Board who is eligible to participate in the Plan may be a
               member of the Committee.

     c)   Rule 16b-3 Limitations. Notwithstanding the provisions of Subsection
          (a) of this Section 13, in the event that Rule 16b-3 promulgated under
          the Securities Exchange Act of 1934, as amended (the "Exchange Act"),
          or any successor provision ("Rule 16b-3") provides specific
          requirements for the administrators of plans of this type, the Plan
          shall be only administered by such a body and in such a manner as
          shall comply with the applicable requirements of Rule 16b-3. Unless
          permitted by Rule 16b-3, no discretion concerning decisions regarding
          the Plan shall be afforded to any committee or person that is not
          "disinterested" as that term is used in Rule 16b-3.

14.  Designation of Beneficiary.
     --------------------------

     a)   The beneficiary(ies) designated by the participant to take under the
          life insurance program of the Company, or a beneficiary chosen by a
          participant is written designation to the Company of a beneficiary
          shall receive any shares and cash, if any, from the participant's
          account under the Plan in the event of such participant's death
          subsequent to an Exercise Date on which the option is exercised but
          prior to delivery to such participant of such shares and cash. In
          addition, the same beneficiary(ies) shall receive any cash from the
          participant's account under the Plan in the event of such
          participant's death prior to exercise of the option.

     b)   Such designation of beneficiary may be changed by the participant at
          any time by written notice. In the event of the death of a participant
          and in the absence of a beneficiary validly designated under the Plan
          who is living at the time of such participant's death, the Company
          shall deliver such shares and/or cash to the executor or administrator
          of the estate of the participant, or if no such executor or
          administrator has been appointed (to the knowledge of the Company),
          the Company, in its discretion, may deliver such shares and/or cash to
          the spouse or to any one or more dependents or relatives of the
          participant, or if no spouse, dependent or relative is known to the
          Company, then to such other person as the Company may designate.

15.  Transferability.
     ---------------

     Neither payroll deductions credited to a participant's account nor any
     rights with regard to the exercise of an option or to receive shares under
     the Plan may be assigned, transferred, pledged or otherwise disposed of in
     any way (other than by will, the laws of descent and distribution or as
     provided in Section 14 hereof) by the participant. Any such attempt at
     assignment, transfer, pledge or other disposition shall be without effect,
     except that the Company may treat such act as an election to withdraw funds
     from an Offering Period in accordance with Section 10 hereof.

16.  Use of Funds.
     ------------

     All payroll deductions received or held by the Company under the Plan may
     be used by the Company for any corporate purpose, and the Company shall not
     be obligated to segregate such payroll deductions.

17.  Reports.
     -------

     Individual accounts will be maintained for each participant in the Plan.
     Statements of account will be given to participating Employees at least
     annually, which statements will set forth the amounts of payroll
     deductions, the Purchase Price, the number of shares purchased and the
     remaining cash balance, if any.

                                    Page 5
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18.  Adjustments Upon Changes in Capitalization.
     ------------------------------------------

     a)  Changes in Capitalization. Subject to any required action by the
         shareholders of the Company, the Reserves as well as the price per
         share of Common Stock covered by each option under the Plan which has
         not yet been exercised shall be proportionately adjusted for any
         increase or decrease in the number of issued shares of Common Stock
         resulting from a stock split, reverse stock split, stock dividend,
         combination or reclassification of the Common Stock, or any other
         increase or decrease in the number of shares of Common Stock effected
         without receipt of consideration by the Company; provided, however,
         that conversion of any convertible securities of the Company shall not
         be deemed to have been "effected without receipt of consideration".
         Such adjustment shall be made by the Board, whose determination in that
         respect shall be final, binding and conclusive. Except as expressly
         provided herein, no issuance by the Company of shares of stock of any
         class, or securities convertible into shares of stock of any class,
         shall affect, and no adjustment by reason thereof shall be made with
         respect to, the number or price of shares of Common Stock subject to an
         option.

     b)  Dissolution or Liquidation. In the event of the proposed dissolution or
         liquidation of the Company, the Offering Period will terminate
         immediately prior to the consummation of such proposed action, unless
         otherwise provided by the Board.

     c)  Merger or Asset Sale. In the event of a proposed sale of all or
         substantially all of the assets of the Company, or the merger of the
         Company with or into another corporation, each option under the Plan
         shall be assumed or an equivalent option shall be substituted by such
         successor corporation or a parent or subsidiary of such successor
         corporation, unless the Board determines, in the exercise of its sole
         discretion and in lieu of such assumption or substitution, to shorten
         the Offering Period then in progress by setting a new Exercise Date
         (the "New Exercise Date") or to cancel each outstanding right to
         purchase and refund all sums collected from participants during the
         Offering Period then in progress. If the Board shortens the Offering
         Period then in progress in lieu of assumption or substitution in the
         event of a merger or sale of assets, the Board shall notify each
         participant in writing, at least ten (10) business days prior to the
         New Exercise Date, that the Exercise Date for his option has been
         changed to the New Exercise Date and that his option will be exercised
         automatically on the New Exercise Date, unless prior to such date he
         has withdrawn from the Offering Period as provided in Section 10
         hereof. For purposes of this paragraph, an option granted under the
         Plan shall be deemed to be assumed if, following the sale of assets or
         merger, the option confers the right to purchase, for each share of
         option stock subject to the option immediately prior to the sale of
         assets or merger, the consideration (whether stock, cash or other
         securities or property) received in the sale of assets or merger by
         holders of Common Stock for each share of Common Stock held on the
         effective date of the transaction (and if such holders were offered a
         choice of consideration, the type of consideration chosen by the
         holders of a majority of the outstanding shares of Common Stock);
         provided, however, that if such consideration received in the sale of
         assets or merger was not solely common stock of the successor
         corporation or its parent (as defined in Section 424(e) of the Code),
         the Board may, with the consent of the successor corporation and the
         participant, provide for the consideration to be received upon exercise
         of the option to be solely common stock of the successor corporation or
         its parent equal in fair market value to the per share consideration
         received by holders of Common Stock and the sale of assets or merger.

     d)  The Board may, if it so determines in the exercise of its sole
         discretion, also make provision for adjusting the Reserves, as well as
         the price per share of Common Stock covered by each outstanding option,
         in the event the Company effects one or more reorganizations,
         recapitalization, rights offerings or other increases or reductions of
         shares of its outstanding Common Stock, and in the event of the Company
         being consolidated with or merged into any other corporation.

19.  Amendment or Termination.
     ------------------------

     a)  The Board of Directors of the Company may at any time and for any
         reason terminate or amend the Plan. Except as provided in Section 18
         hereof, no such termination can affect options previously granted,
         provided that an Offering Period may be terminated by the Board of
         Directors on any Exercise Date if the Board determines that the
         termination of the Plan is in the best interests of the Company and its
         shareholders. Except as provided in Section 18 hereof, no amendment may
         make any change in any option theretofore granted which adversely
         affects the rights of any participant. To the extent necessary to
         comply with Rule 16b-3 or under Section 423 of the Code (or any
         successor rule or provision or any other applicable law or regulation),
         the Company shall obtain shareholder approval in such a manner and to
         such a degree as required.

     b)  Without shareholder consent and without regard to whether any
         participant rights may be considered to have been "adversely affected,"
         the Board (or its committee) shall be entitled to change the Offering
         Periods, limit the frequency and/or number of changes in the amount
         withheld during an Offering Period, establish the exchange ratio
         applicable to amounts withheld in a currency other than U.S. dollars,
         permit payroll withholding in excess of the amount designated by a

                                    Page 6
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         participant in order to adjust for delays or mistakes in the Company's
         processing of properly completed withholding elections, establish
         reasonable waiting and adjustment periods and/or accounting and
         crediting procedures to ensure that amounts applied toward the purchase
         of Common Stock for each participant properly correspond with amounts
         withheld from the participant's Compensation, and establish such other
         limitations or procedures as the Board (or its committee) determines in
         its sole discretion advisable which are consistent with the Plan.

20.  Notices.
     -------

     All notices or other communications by a participant to the Company under
     or in connection with the Plan shall be deemed to have been duly given when
     received in the form specified by the Company at the location, or by the
     person, designated by the Company for the receipt thereof.

21.  Conditions Upon Issuance of Shares.
     ----------------------------------

     Shares shall not be issued with respect to an option unless the exercise of
     such option and the issuance and delivery of such shares pursuant thereto
     shall comply with all applicable provisions of law, domestic or foreign,
     including, without limitation, the Securities Act of 1933, as amended, the
     Securities Exchange Act of 1934, as amended, the rules and regulations
     promulgated thereunder, and the requirements of any stock exchange upon
     which the shares may then be listed, and shall be further subject to the
     approval of counsel for the Company with respect to such compliance.

     As a condition to the exercise of an option, the Company may require the
     person exercising such option to represent and warrant at the time of any
     such exercise that the shares are being purchased only for investment and
     without any present intention to sell or distribute such shares if, in the
     opinion of counsel for the Company, such a representation is required by
     any of the aforementioned applicable provisions of law.

22.  Term of Plan.
     ------------

     The Plan shall become effective upon the earlier to occur of its adoption
     by the Board of Directors or its approval by the shareholders of the
     Company. It shall continue in effect for a term of ten (10) years unless
     sooner terminated under Section 19 hereof.

23.  Additional Restrictions of Rule 16b-3.
     -------------------------------------

     The terms and conditions of options granted hereunder to, and the purchase
     of shares by, persons subject to Section 16 of the Exchange Act shall
     comply with the applicable provisions of Rule 16b-3. This Plan shall be
     deemed to contain, and such options shall contain, and the shares issued
     upon exercise thereof shall be subject to, such additional conditions and
     restrictions as may be required by Rule 16b-3 to qualify for the maximum
     exemption from Section 16 of the exchange Act with respect to Plan
     transactions.

                                    Page 7Exhibit 10.1

                                       September 29, 2000

Acqua Wellington North American Equities Fund, Ltd.
c/o Fortis Fund Services (Bahamas) Limited
Montague Sterling Centre
East Bay Street, P.O. Box SS-6238
Nassau, Bahamas

Dear Sirs:

      This  letter  sets forth the  agreement  between  Acqua  Wellington  North
American  Equities Fund, Ltd. (the  "Purchaser")  and Cytogen  Corporation  (the
"Company")  regarding  the  purchase  by the  Purchaser  from the Company of the
Company's  common  stock (the "Common  Stock") on the date  hereof.  The parties
agree as follows:

      This Agreement  relates to the purchase by the Purchaser of 902,601 shares
(the "Shares") of the Company's Common Stock for an aggregate  purchase price of
$6,000,000, which purchase is being settled by the parties on the date hereof.

      The Company is a corporation  duly  incorporated,  validly existing and in
good  standing  under  the  laws of  Delaware.  The  Company  has the  requisite
corporate  power and  authority to enter into and perform this  Agreement and to
issue and sell the Shares in accordance  with the terms hereof.  The  execution,
delivery and  performance of this Agreement by the Company and the  consummation
by it of the  transactions  contemplated  hereby  have  been  duly  and  validly
authorized  by all  necessary  corporate  action.  A copy of the  duly  executed
resolutions  of the Board of  Directors  of the  Company is  attached  hereto as
Exhibit "B".  This  Agreement  has been duly executed and delivered on behalf of
the Company by a duly authorized  officer. A copy of a duly executed  incumbency
certificate  of the Company's  duly  authorized  officers is attached  hereto as
Exhibit "C". This Agreement  constitutes,  or shall constitute when executed and
delivered, a valid and binding obligation of the Company enforceable against the
Company in accordance with its terms.

      The Shares have been duly  authorized  by all necessary  corporate  action
and,  when paid for or issued in accordance  with the terms  hereof,  the Shares
shall be validly issued and outstanding,  fully paid and nonassessable,  and the
Purchaser shall be entitled to all rights accorded to a holder of Common Stock.

      The  Company  represents  and  warrants  that  (a) the  Shares  have  been
registered under the Securities Act of 1933, as amended (the "Securities  Act"),
pursuant  to a  registration  statement  on Form  S-3,  Commission  File  Number
333-33436  (the  "Registration  Statement");  and (b) the  Company  has  filed a
prospectus   supplement  to  the   Registration   Statement   (the   "Prospectus
Supplement") in connection  with this  transaction.  Copies of the  Registration
Statement and the Prospectus  Supplement,  each as filed and, in the case of the
Registration  Statement,  declared  effective  by the  Securities  and  Exchange
Commission, are annexed hereto as Exhibits "D" and "E", respectively.

      The Company has taken all action  necessary on its part to list the Shares
for  trading  on the  Nasdaq  system  or  any  relevant  market  or  system,  if
applicable. A copy of the Company's listing application with Nasdaq or any other
relevant market or system is attached hereto as Exhibit "F."

      The Company  will  continue to take all action  necessary  to continue the
listing  or trading of its  Common  Stock on the Nasdaq  National  Market or any
relevant market or system,  if applicable,  and will comply in all respects with
the Company's reporting, listing (including,  without limitation, the listing of
the Shares) or other  obligations  under the rules of the Nasdaq National Market
or any relevant market or system.

      The Company has  delivered  or made  available to the  Purchaser  true and
complete  copies of the filings on Forms 10-K, 10-Q and 8-K filed by the Company
with the Securities and Exchange  Commission since March 28, 2000 (collectively,
the  "Commission  Filings").  The Company has not provided to the  Purchaser any
information which, according to applicable law, rule or regulation,  should have
been  disclosed  publicly by the  Company  but

                                     - 1 -

<PAGE>

which has not been so  disclosed,  other than with  respect to the  transactions
contemplated  by this  Agreement.  As of  their  respective  dates,  each of the
Commission  Filings  complied in all material  respects with the requirements of
the  Securities  Exchange  Act of 1934  (the  "Exchange  Act") and the rules and
regulations of the Commission  promulgated  thereunder and other federal,  state
and local laws, rules and regulations  applicable to such documents,  and, as of
their  respective  dates,  none of the  Commission  Filings  referred  to  above
contained any untrue statement of a material fact or omitted to state a material
fact required to be stated  therein or necessary in order to make the statements
therein,  in  light  of the  circumstances  under  which  they  were  made,  not
misleading.  The financial  statements of the Company included in the Commission
Filings comply as to form in all material  respects with  applicable  accounting
requirements  and the published rules and regulations of the Commission or other
applicable rules and regulations with respect thereto.  No event or circumstance
has occurred or exists with respect to the Company or its  subsidiaries or their
respective businesses, properties, prospects, operations or financial condition,
which,  under applicable law, rule or regulation,  requires public disclosure or
announcement  by the  Company but which has not been so  publicly  announced  or
disclosed.

      The Company will  promptly  notify the  Purchaser of (a) any stop order or
other suspension of the effectiveness of the Registration  Statement and (b) the
happening  of any  event as a result  of which the  prospectus  included  in the
Registration  Statement includes an untrue statement of a material fact or omits
to state a material fact required to be stated therein, or necessary to make the
statements  therein,  in light of the circumstances  under which they were made,
not misleading.

      The Company may issue a press release or otherwise make a public statement
or announcement  with respect to the completion of the transaction  contemplated
hereby; without the prior consent of the Purchaser.

      The Company and the  Purchaser  will  indemnify  each other as provided in
Exhibit "A" attached hereto against  liability with respect to the  Registration
Statement (including, without limitation, the Prospectus Supplement) relating to
the Shares which was sold by the Company to the Purchaser.  For purposes of said
Exhibit A, capitalized terms used therein without definition shall have the same
meanings therein as are ascribed to said terms in this agreement.

      This  Agreement and the legal  relations  between the parties  hereto with
respect to any  purchase of Common  Stock by the  Purchaser  hereunder  shall be
governed and construed in accordance with the  substantive  laws of the State of
New York without giving effect to the conflicts of law principles thereunder.

      Delivery of an  executed  copy of a signature  page to this  Agreement  by
facsimile  transmission  shall be effective  as delivery of a manually  executed
copy of this Agreement and shall be effective and enforceable as the original.

      Please  execute  a  copy  of  this  letter  which,  when  executed  by the
Purchaser, will constitute an agreement between the Company and the Purchaser.

                                       Very truly yours,

                                       CYTOGEN CORPORATION

                                       By:  /s/ H. Joseph Reiser
                                            -------------------------
                                            Name:  H. Joseph Reiser
                                            Title: President and Chief
                                                   Executive Officer

AGREED TO:

PURCHASER:

ACQUA WELLINGTON NORTH
AMERICAN EQUITIES FUND, LTD.

By:  /s/ Anthony L. M. Inder Rieden
     ----------------------------------
      Name:  Anthony L. M. Inder Rieden
      Title: Director

                                      - 2 -

<PAGE>

EXHIBIT 'A'

                            TERMS OF INDEMNIFICATION

(1)   INDEMNIFICATION  BY THE  COMPANY.  The  Company  will  indemnify  and hold
      harmless the Purchaser and each person, if any, who controls the Purchaser
      within the meaning of Section 15 of the Securities Act of 1933, as amended
      (the "Securities  Act"); or Section 20(a) of the Securities  Exchange Act,
      as amended  (the  "Exchange  Act");  from and against any losses,  claims,
      damages, liabilities,  costs and expenses (including,  without limitation,
      reasonable costs of defense and  investigation and all attorneys' fees and
      expenses) to which the Purchaser and each person, if any, who controls the
      Purchaser  may become  subject,  under the  Securities  Act or  otherwise,
      insofar as such  losses,  claims,  damages,  liabilities  and expenses (or
      actions in respect thereof) arise out of; or are based upon (i) any untrue
      statement or alleged  untrue  statement of a material fact  contained,  or
      incorporated  by  reference,  in the  Registration  Statement  relating to
      Shares being sold to the Purchaser  (including the  prospectus  dated June
      14, 2000,  and the  prospectus  supplement  dated  September 29, 2000 (the
      "Prospectus  Supplement") which are a part of the Registration Statement),
      or any amendment or supplement to the Registration  Statement, or (ii) the
      omission or alleged  omission to state in that  Registration  Statement or
      any document  incorporated by reference in the Registration  Statement,  a
      material  fact  required  to be stated  therein or  necessary  to make the
      statements therein not misleading (an "Indemnifiable Matter").

      The Company will reimburse the Purchaser and each such controlling  person
      promptly  upon demand for any legal or other costs or expenses  reasonably
      incurred by the  Purchaser  or the  controlling  person in  investigating,
      defending against, or preparing to defend against any claim relating to an
      Indemnifiable  Matter,  except that the Company  will not be liable to the
      extent such claim,  suit or  proceeding  which  results in a loss,  claim,
      damage,  liability or expense  arises out of, or is based upon,  an untrue
      statement,  alleged  untrue  statement,   omission  or  alleged  omission,
      included in any  Prospectus  Supplement  or any amendment or supplement to
      the  Prospectus  Supplement  in reliance  upon,  and in  conformity  with,
      written  information  furnished  by  the  Purchaser  to  the  Company  for
      inclusion in the Prospectus Supplement.

(2)   INDEMNIFICATION  PROCEDURES.  Promptly after a person receives notice of a
      claim or the  commencement of an action,  suit or proceeding for which the
      person  intends to seek  indemnification  under  Paragraph (a) or (b), the
      person  will  notify  the  indemnifying  party in  writing of the claim or
      commencement of the action, suit or proceeding,  but failure to notify the
      indemnifying  party will not relieve the indemnifying party from liability
      under  Paragraph (a) or (b), except to the extent the  indemnifying  party
      has  been  materially  prejudiced  by the  failure  to  give  notice.  The
      indemnifying  party will be entitled to  participate in the defense of any
      claim,  action,  suit or proceeding as to which  indemnification  is being
      sought,  and  if  the  indemnifying  party  acknowledges  in  writing  the
      obligation to indemnify the party against whom the claim,  action, suit or
      proceeding  is  brought,  the  indemnifying  party  may  (but  will not be
      required  to) assume  the  defense  against  the  claim,  action,  suit or
      proceeding with legal counsel chosen by the indemnifying  party.  After an
      indemnifying  party  notifies an indemnified  party that the  indemnifying
      party wishes to assume the defense of a claim,  action, suit or proceeding
      the indemnifying  party will not be liable for any legal or other expenses
      incurred by the  indemnified  party in connection with the defense against
      the claim,  action, suit or proceeding,  except that if, in the opinion of
      legal counsel to the  indemnifying  party,  one or more of the indemnified
      parties  should be  separately  represented  in  connection  with a claim,
      action,  suit or proceeding the  indemnifying  party will pay the fees and
      expenses  of one  separate  counsel  for  the  indemnified  parties.  Each
      indemnified party, as a condition  precedent to receiving  indemnification
      as provided in Paragraph (a) or (b),  will, at the cost and expense of the
      indemnifying  party,   cooperate  in  all  reasonable  respects  with  the
      indemnifying party in the defense of the claim, action, suit or proceeding
      as to which  indemnification  is  sought.  No  indemnifying  party will be
      liable  for any  settlement  of any  claim,  action,  suit  or  proceeding
      effected  without its prior written consent.  No indemnifying  party will,
      without the prior written  consent of the  indemnified  party,  effect any
      settlement of a pending or  threatened  claim,  action or proceeding  with
      respect which an indemnified party is, or is informed that it may be, made
      a party and for which it would be entitled to indemnification,  unless the
      settlement includes an unconditional release of the indemnified party from
      all  liability  and claims which are the subject  matter of the pending or
      threatened action.

                                     - 3 -

<PAGE>

(3)   CONTRIBUTION.  If for any reason the indemnification  provided for in this
      agreement is not available to, or is not sufficient to hold  harmless,  an
      indemnified party in respect of any loss, claim, damage,  liability,  cost
      or expense  referred to in Paragraph (a) or (b), each  indemnifying  party
      will, in lieu of  indemnifying  the indemnified  party,  contribute to the
      amount paid or payable by the  indemnified  party as a result of the loss,
      claim, damage,  liability,  cost or expense (i) in the proportion which is
      appropriate to reflect the relative  benefits received by the indemnifying
      party, on the one hand, and by the  indemnified  party, on the other hand,
      from the sale of stock which is the subject of the claim,  action, suit or
      proceeding which resulted in the loss, claim,  liability,  cost or expense
      or (ii) if that  allocation is not  permitted by  applicable  law, in such
      proportion as is appropriate to reflect not only the relative  benefits of
      the sale of stock, but also the relative fault of the  indemnifying  party
      and the  indemnified  party with  respect to the  statements  or omissions
      which are the  subject  of the  claim,  action,  suit or  proceeding  that
      resulted in the loss, claim, damage, liability, cost or expense as well as
      any other relevant equitable considerations.

                                     - 4 -

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