Exhibit 99.6

                          IMCLONE SYSTEMS INCORPORATED

                1996 NON-QUALIFIED STOCK OPTION PLAN, AS AMENDED(1)


                                    ARTICLE I

                                 Purpose of Plan

         1.1 General Purpose. The purpose of this Non-Qualified Stock Option
Plan (the "Plan") is to promote the interests of ImClone Systems Incorporated
(the "Company") by affording key consultants, advisors, directors and employees
an opportunity to acquire a proprietary interest in the Company pursuant to
stock options issued by the Company, and thus to create in such persons
increased personal interest in its continued success.

         1.2 Statutory Stock Option. Options granted under the Plan are intended
to be "non-qualified" stock options under the Internal Revenue Code of 1986, as
amended (the "Code").

                                   ARTICLE II

                             Shares Subject to Plan

         2.1 Description of Shares. Subject to Article VIII hereof, the stock to
which the Plan applies is shares of the Company's common stock, $.001 par value
("Common Stock"), either authorized but unissued or Treasury shares. The number
of shares of Common Stock to be issued or sold pursuant to options granted
hereunder shall not exceed 4,000,000 shares; provided,

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         1 This plan was adopted by the Board on February 25, 1996 and approved
by the stockholders on June 3, 1996; it was amended by the Board on April 3,
1997 and such amendments were ratified by the stockholders on June 3, 1997; it
was amended by the Board on March 29, 1999 and such amendments were ratified by
the stockholders on May 24, 1999.


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         that such number shall be reduced by the number of shares which have
been sold under, or may be sold pursuant to options granted from time to time
under, the Company's 1996 Incentive Stock Option Plan (the "Incentive Stock
Option Plan") to the same extent as if such sales had been made or options had
been granted pursuant to this Plan.

         2.2 Restoration of Unpurchased Shares. Any shares subject to an option
granted hereunder that, for any reason, expires or is terminated unexercised as
to such shares may again be subject to an option to be granted hereunder.

                                   ARTICLE III

                     Administration; Committees; Amendments

         3.1 Administration. The Plan shall be administered by any of the
Compensation Committee, the Stock Option Committee (which is a subcommittee of
the Compensation Committee) (collectively, the "Committees") or the Board of
Directors of the Company (the "Board"). The Committees shall be comprised of not
less than two persons who shall be appointed by the Board from among the members
of the Board. Members of the Committees and the Board shall be eligible to
become participants under the Plans and may receive discretionary and
non-discretionary grants of options.

         3.2 Duration; Removal; Etc. The members of the Committees shall serve
at the pleasure of the Board, which shall have the power at all times to remove
members from the Committees or to add members thereto. Vacancies in the
Committees, however caused, shall be filled by action of the Board.


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         3.3 Meetings; Actions of Committee. Each of the Committees may select
one of its members as its Chairman and shall hold its meetings at such times and
places as it may determine. All decisions or determinations of the Committees
and the Board shall be made by the majority vote or decision of all of its
members, whether present at a meeting or not; provided, however, that any
decision or determination reduced to writing and signed by all of the members
shall be as fully effective as if this had been made at a meeting duly called
and held. Each of the Committees and the Board may make such rules and
regulations for the conduct of its business not inconsistent herewith as it may
deem advisable.

         3.4 Interpretation. The interpretation and construction by any of the
Committees or the Board of the provisions of the Plan or of the options granted
hereunder shall be final, unless in the case of the Committees otherwise
determined by the Board. No member of the Board or of the Committees shall be
liable for an action taken or determination made in good faith.

         3.5 Amendments or Discontinuation. The Board may make such amendments,
changes, and additions to the Plan, or may discontinue and terminate the Plan,
as it may deem advisable from time to time; provided, however, that no action
shall affect or impair any options theretofore granted under the Plan, and
provided, further, however, that the affirmative vote of the owners of a
majority of the outstanding shares of Common Stock present at a meeting in
person or by proxy and entitled to vote shall be necessary to effect any
amendment to the Plan which would increase the number of shares of Common Stock
subject to options granted under the Plan.


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                                   ARTICLE IV

                  Participants; Maximum Grant; Duration of Plan

         4.1 Eligibility and Participation. Options shall be granted only to
persons ("Participants") who at the time of granting are key consultants,
advisors, directors or employees of the Company. Any of the Committees or the
Board shall determine the key consultants, advisors, directors and employees to
be granted options hereunder, the number of shares of Common Stock subject to
such options, the exercise prices of options, the terms thereof and any other
provisions not inconsistent with the Plan.

         4.2 Guidelines for Participation. In selecting Participants and
determining the numbers of shares of Common Stock for which options are to be
granted, any of the Committees or the Board shall consult with officers and
directors of the Company, and shall take into account the duties of the
respective persons, their present and potential contributions to the success of
the Company, and such other factors as any of the Committees or the Board shall
deem relevant.

         4.3 Duration of Plan. All options under the Plan shall be granted
within ten years from the date the Plan is approved by the shareholders of the
Company.


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                                    ARTICLE V

                         Terms and Conditions of Options

         5.1 Individual Stock Option Agreements. All stock options granted
pursuant to the Plan shall be evidenced by stock option agreements ("Stock
Option Agreements"), which need not be identical, between the Company and the
Participant in such form as any of the Committees or the Board shall from time
to time approve, subject to the terms of the Plan.

         5.2 Number of Shares. Each Stock Option Agreement shall state the total
number of shares of Common Stock with respect to which the option is granted,
the terms and conditions of the option, and the exercise price or prices
thereof, it being understood that any of the Committees or the Board shall,
subject to the terms of Article VII hereof, have authority to prescribe in any
Stock Option Agreement that the option evidenced thereby may be exercisable in
full or in part, as to any number of shares subject thereto, at any time or from
time to time during said term as any of the Committees or the Board may
determine; provided that no option granted pursuant to the Plan shall be
exercisable after the expiration of ten years from the date such option is
granted. Except as otherwise provided in any Stock Option Agreement, an option
may be exercised at any time or from time to time during the term of the option
as to any or all full (but no fractional) shares which have become purchasable
under such option. Subject to the terms of Article VII hereof, any of the
Committees or the Board shall have the right to accelerate, in whole or in part,
from time to time, conditionally or unconditionally, the right to exercise any
option granted hereunder.


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         5.3 Option Price. Subject to the terms of Article VII hereof, the price
at which the shares of Common Stock subject to each option granted under this
Plan may be purchased (the "option price" or "exercise price") shall be
determined by any of the Committees or the Board, which shall have the authority
at the time the option is granted to prescribe in any Stock Option Agreement
that the price per share, with the passage of pre-determined periods of time,
shall increase from the original price to higher prices.

         5.4 Method of Exercising Option; Full Payment. Subject to the terms of
Article VII hereof and Section 6.1 and Section 6.2 hereof, options granted
pursuant to the Plan may be exercised only if the Participant was, at all times
during the period beginning on the date the option was granted and ending on the
date of such exercise, a key consultant, advisor, director or employee of the
Company. Options shall be exercised by written notice to the Company, addressed
to the Company at its principal place of business. Such notice shall state the
Participant's election to exercise the option and the number of shares of Common
Stock in respect of which it is being exercised, and shall be signed by the
Participant so exercising the option. Such notice shall be accompanied by (a)
the Stock Option Agreement (which, if not exercised for all the shares subject
thereto, shall be appropriately endorsed and returned to the Participant); (b)
payment of the full purchase price of such shares, which payment shall be in
cash, by check or in stock of the Company that has been owned by the Participant
for at least six months, or notes of the Company or, as agreed to by the Board,
other consideration; and such written representations and other documents as may
be desirable, in the opinion of the Company's legal counsel, for purposes of
compliance with state or Federal securities or other laws. In the case of
payment made in stock of the Company, the stock shall be valued at its Fair


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Market Value (as hereinafter defined) on the last business day prior to the date
of exercise. The term "Fair Market Value" for the Common Stock on any particular
date shall mean the last reported sale price of the Common Stock on the
principal market on which the Common Stock trades on such date or, if no trades
of Common Stock are made or reported on such date, then on the next preceding
date on which the Common Stock traded. The Company shall deliver a certificate
or certificates representing shares of Common Stock purchased pursuant to such
notice to the purchaser as soon as practicable after receipt of such notice,
subject to Article IX hereof. Any of the Committees or the Board may amend an
already outstanding Stock Option Agreement to add a provision permitted by
clause (b) of this Section 5.4, and no such amendment, by itself, shall be
deemed to constitute the grant of a new option for purposes of this Plan.

         5.5 Rights as a Shareholder. No Participant shall have any rights as a
shareholder with respect to shares of Common Stock subject to an option granted
under the Plan until the date of the issuance to such Participant of a stock
certificate in respect of such shares. No adjustment shall be made for dividends
or other rights for which the record date is prior to the date such stock
certificate is issued.

         5.6 Other Provisions. Stock Option Agreements entered into pursuant to
the Plan may contain such other provisions (not inconsistent with the Plan) as
any of the Committees or the Board may deem necessary or desirable, including,
but not limited to, covenants on the part of the Participant not to compete, not
to sell Common Stock obtained from the exercise of options for specified periods
of time, and remedies available to the Company in the event of the breach of any
such covenant.


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                                   ARTICLE VI

                          Termination; Transferability

         6.1 Termination. Except as otherwise provided in connection with the
grant of any option or the termination of any Participant, the right to exercise
any unexercised portion of any option granted under the Plan shall terminate on
the date of termination of the relationship between the Participant and the
Company, for any reason, without regard to cause, other than by reason of death
or disability. The option may not be exercised thereafter, and the shares of
Common Stock subject to the unexercised portion of such option may again be
subject to new options under the Plan. Such restrictions shall not apply to the
options granted pursuant to Article VII which shall be exercisable in accordance
with the terms thereof.

         6.2 Death or Disability of Participant. Except as otherwise permitted
in connection with the grant of any option or the death or disability of a
Participant, in the event a Participant dies or is disabled while he is a
consultant, advisor, director or employee of the Company, any options
theretofore granted to him shall be exercisable only within the next 12 months
immediately succeeding such death or disability and then only (a) in the case of
death, by the person or persons to whom the Participants rights under the option
shall pass by will or the laws of descent and distribution, and in the case of
disability, by such Participant or his legal representative, and (b) if and to
the extent that he was entitled to exercise the option at the date of his death
or disability. Such restrictions shall not apply to the options of Participating
Directors which shall be exercisable in accordance with the terms set forth in
Article VII hereof.

         6.3 Transferability. Options granted to a Participant under the Plan
shall not be transferable otherwise than by will, by the laws of descent and
distribution, or (if authorized in


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the applicable Stock Option Agreement) pursuant to a qualified domestic
relations order ("QDRO") as defined by the Internal Revenue Code of 1986, as
amended, or Title I of the Employee Retirement Income Security Act of 1974, as
amended, or the rules thereunder. During the Participant's lifetime, options
shall be exercised only by such Participant, such Participant's guardian or
legal representative, or (if authorized in the applicable Stock Option
Agreement) such Participant's transferee pursuant to a QDRO.

                                   ARTICLE VII

                                Directors' Grants

         7.1 Eligibility. Annually, on February 15 of each of the Company's
Fiscal Years, any Director of the Company who at the time is not a full-time
employee of the Company (a "Participating Director"), shall be granted an option
for 15,000 shares of Common Stock, except that the Chairman who is not a
full-time employee of the Company shall be granted an option for 30,000 shares
of Common Stock. Each person who becomes a Participating Director after the
first day of the Company's fiscal year and within nine months of that date shall
be granted, on the date that person becomes a Participating Director, an option
for a number of shares of Common Stock determined by pro rating the normal
15,000 share annual amount (or 30,000 if the Chairman) based on the period of
time remaining in the fiscal year in which such person becomes a Participating
Director. No person who owns 10% or more of the outstanding Common Stock of the
Company (including shares of Common Stock issuable upon exercise of outstanding
options and warrants), shall be granted options under this Article. Options
under this Article are non-discretionary.


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         7.2 Options Terms. Options granted under this Article VII shall not be
exercisable until the date upon which the option holder has provided one year of
continuous service as a Participating Director following the date of grant of
such option. Options granted pursuant to this Article shall have an exercise
price equal to the Fair Market Value (as hereinafter defined) of the Common
Stock on the date of the grant. The term "Fair Market Value" for the Common
Stock on any particular date shall mean the last reported sale price of the
Common Stock on the principal market on which the Common Stock trades on such
date or, if no trades of Common Stock are made or reported on such date, then on
the next preceding date on which the Common Stock traded. Notwithstanding any
other provisions of this Plan, options granted under this Article shall remain
exercisable for ten years after the date of grant and the option holder (or his
legal representative or that of his estate) may continue to exercise an option
notwithstanding that the holder ceases to be a Participating Director.

         7.3 Other Provisions. In all other respects, Options granted under this
Article VII shall be subject to the other provisions of the Plan, including but
not limited to those governing method of exercise, exercise payment, tax
withholding, and transferability. Notwithstanding any other provisions of this
Plan, the provisions of this Article VII may not be amended more than once every
six months, other than to comport with changes in the Code.

                                  ARTICLE VIII

                               Capital Adjustments

         8.1 Capital Adjustments. If any change is made in the shares of Common
Stock subject to the Plan or subject to any option granted under the Plan
(through merger, consolidation,


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reorganization, recapitalization, stock dividend, split-up, combination of
shares, exchange of shares, issuance of rights to subscribe, or change in
capital structure), appropriate adjustments shall be made by any of the
Committees or the Board as to the maximum number of shares subject to the Plan
and the number of shares and price per share subject to outstanding options as
shall be equitable to prevent dilution or enlargement of option rights. Any
determination made by any of the Committees or the Board under this Article VIII
shall be final, binding and conclusive upon each Participant.

                                   ARTICLE IX

                            Legal Requirements, Etc.

         9.1 Revenue Stamps. The Company shall be responsible and shall pay for
any transfer, revenue, or documentary stamps with respect to shares issued upon
the exercise of options granted under the Plan.

         9.2 Legal Requirements. The Company shall not be required to issue
certificates for shares upon the exercise of any option unless and until, in the
opinion of the Company's legal counsel, such issuance would not result in a
violation of any state or Federal securities or other law. Certificates for
shares, when issued, shall have, if required in the opinion of the Company's
legal counsel, the following legend, or statements of other restrictions,
endorsed thereon, and may not immediately be transferable:

         The shares of Common Stock evidenced by this certificate have been
         issued to the registered owner in reliance upon written representations
         that these shares have been purchased for investment. These shares may
         not be sold, transferred, or assigned unless, in the opinion of the
         Company and its legal counsel, such sale, transfer, or assignment will
         not be in violation of the Securities Act of 1933, as


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         amended, applicable rules and regulations of the Securities and
         Exchange Commission and any applicable state securities laws.

         9.3 Private Offering. The options to be granted under the Plan are
available only to a limited number of present and future key consultants,
advisors, directors and employees of the Company who have knowledge of the
Company's financial condition, management, and affairs. Such options are not
intended to provide additional capital for the Company, but are to encourage
stock ownership by the Company's key personnel. By the act of accepting an
option, in the absence of an effective registration statement under the
Securities Act of 1933, as amended, Participants shall agree that upon exercise
of such option, they will acquire the shares of Common Stock that are the
subject thereof for investment and not with any intention at such time to resell
or redistribute the same, and they shall confirm such agreement at the time of
exercise, but the neglect or failure to confirm the same in writing shall not be
a limitation of such agreement.


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                                    ARTICLE X

                                     General

         10.1 Application of Funds. The proceeds received by the Company from
the sale of shares of Common Stock pursuant to the exercise of options therefor
shall be used for general corporate purposes.

         10.2 Right of the Company to Terminate Relationship. Nothing contained
in the Plan or in a Stock Option Agreement shall confer upon any Participant any
right to be continued as a consultant, advisor, director or employee of the
Company, or interfere in any way with the right of the Company to terminate such
relationship for any reason whatsoever, with or without cause, at any time.

         10.3 No Obligation to Exercise. The granting of an option hereunder
shall impose no obligation upon the Participant to exercise such option.

         10.4 Effectiveness of Plan. The Plan shall become effective upon its
adoption by the Board. Options may be granted under the Plan prior to the
approval of the Plan by the Shareholders, but no such option may be exercised
prior to such approval.

         10.5 Other Benefits. Participation in the Plan shall not preclude a
Participant from eligibility in any other stock benefit plan of the Company or
any old age benefit, insurance, pension, profit sharing, retirement, bonus or
other plan which the Company has adopted, or may, at any time, adopt.

         10.6 Tax Requirements. The exercise or surrender of any option under
this Plan shall constitute a Participant's full and complete consent to whatever
action any of the Committees or


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the Board elect to satisfy the Federal and state withholding requirements, if
any, which the Committee in its discretion deems applicable to such exercise.

         10.7 Interpretations and Adjustments. To the extent permitted by Law,
an interpretation of the Plan and a decision on any matter within any of the
Committees' or the Board's discretion made in good faith is binding on all
persons. A misstatement or other mistake of fact shall be corrected when it
becomes known, and the person responsible shall make such adjustment on account
thereof as he considers equitable and practicable.

         10.8 Information. The Company shall, upon request or as may be
specifically required hereunder, furnish or cause to be furnished, all of the
information or documentation which is necessary or required by any of the
Committees or the Board to perform its duties and functions under the Plan.

         10.9 Governing Law. The Plan and any and all options granted thereunder
shall be governed by, and construed and enforced in accordance with, the laws of
the State of New York from time to time in effect.

         10.10 Certain Definitions.

         10.10.1 "Parent". The term "parent" shall mean a "parent corporation"
as defined in Section 424(e) of the Code.

         10.10.2 "Subsidiary". The term "subsidiary" shall mean a "subsidiary
corporation" as defined in Section 424(f) of the Code.

         10.10.3 "Disabled". The term "disabled" shall have the definition set
forth in Section 22(a) (3) of the Code.


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