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                                                                     Exhibit 4.2

                                                                  EXECUTION COPY


                                  Medarex, Inc.

                     4.25% Convertible Senior Notes due 2010

                          Registration Rights Agreement

                                                      July 23, 2003

Goldman, Sachs & Co.,
UBS Financial Services, Inc.
J.P. Morgan Securities Inc.
Bear, Stearns & Co. Inc.
As representatives of the several Purchasers
   named in Schedule I to the Purchase Agreement
c/o Goldman, Sachs & Co.
85 Broad Street
New York, New York 10004

Ladies and Gentlemen:

     Medarex, Inc., a New Jersey corporation (the "Company"), proposes to issue
and sell to the Purchasers (as defined herein) upon the terms set forth in the
Purchase Agreement (as defined herein) an aggregate of $125,000,000 principal
amount of 4.25% Convertible Series Notes due 2010 ("Convertible Notes"),
convertible into shares of Common Stock, (the Convertible Notes and Common Stock
are collectively referred to herein as "Securities"). As an inducement to the
Purchasers to enter into the Purchase Agreement and in satisfaction of a
condition to the obligations of the Purchasers thereunder, the Company agrees
with the Purchasers for the benefit of Holders (as defined herein) from time to
time of the Registrable Securities (as defined herein) as follows:

     1.   Definitions.

     (a)  Capitalized terms used herein without definition shall have the
meanings ascribed to them in the Purchase Agreement. As used in this Agreement,
the following defined terms shall have the following meanings:

     "Affiliate" of any specified person means any other person which, directly
or indirectly, is in control of, is controlled by, or is under common control
with such specified person. For purposes of this definition, control of a person
means the power, direct or indirect, to direct or cause the direction of the
management and policies of such person whether by contract or otherwise; and the
terms "controlling" and "controlled" have meanings correlative to the foregoing.

     "Closing Date" means the First Time of Delivery as defined in the Purchase
Agreement.

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     "Commission" means the United States Securities and Exchange Commission, or
any other federal agency at the time administering the Exchange Act or the
Securities Act, whichever is the relevant statute for the particular purpose.

     "Common Stock" means the Company's common stock, par value $.01 per share
together with any associated preferred share purchase rights.

     "DTC" means The Depository Trust Company.

     "Effective Date" has the meaning assigned thereto in Section 2(b)(i)
hereof.

     "Effective Failure" has the meaning assigned thereto in Section 7(b)
hereof.

     "Effectiveness Period" has the meaning assigned thereto in Section 2(b)(i)
hereof.

     "Effective Time" means the time at which the Commission declares the Shelf
Registration Statement effective or at which the Shelf Registration Statement
otherwise becomes effective.

     "Electing Holder" has the meaning assigned thereto in Section 3(a)(iii)
hereof.

     "Exchange Act" means the United States Securities Exchange Act of 1934, as
amended.

     "Holder" means any person that is the record owner of Registrable
Securities (and includes any person that has a beneficial interest in any
Registrable Security in book-entry form).

     "Indenture" means the Indenture, dated as of July 23, 2003, between the
Company and Wilmington Trust Company, as amended and supplemented from time to
time in accordance with its terms.

     "Liquidated Damages" has the meaning assigned thereto in Section 7(a)
hereof.

     "Managing Underwriters" means the investment banker or investment bankers
and manager or managers that shall administer an underwritten offering, if any,
conducted pursuant to Section 6 hereof.

     "NASD Rules" means the Rules of the National Association of Securities
Dealers, Inc., as amended from time to time.

     "Notice and Questionnaire" means a Notice of Registration Statement and
Selling Securityholder Questionnaire substantially in the form of Appendix A
hereto.

     The term "person" means an individual, partnership, corporation, limited
liability company, trust or unincorporated organization, or a government or
agency or political subdivision thereof.

     "Prospectus" means the prospectus (including, without limitation, any
preliminary prospectus, any final prospectus and any prospectus that discloses
information previously omitted from a prospectus filed as part of an effective
registration statement in reliance upon

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Rule 430A under the Securities Act) included in the Shelf Registration
Statement, as amended or supplemented by any prospectus supplement with respect
to the terms of the offering of any portion of the Registrable Securities
covered by the Shelf Registration Statement and by all other amendments and
supplements to such prospectus, including all material incorporated by reference
in such prospectus and all documents filed after the date of such prospectus by
the Company under the Exchange Act and incorporated by reference therein.

     "Purchase Agreement" means the purchase agreement, dated as of July 17,
2003 between the Purchasers and the Company relating to the Securities.

     "Purchasers" means the Purchasers named in Schedule I to the Purchase
Agreement.

     "Registrable Securities" means all or any portion of the Securities issued
from time to time under the Indenture in registered form and the shares of
Common Stock issued or issuable upon conversion, repurchase or redemption of
such Securities; provided, however, that a security ceases to be a Registrable
Security when it is no longer a Restricted Security.

     "Registration Default" has the meaning assigned thereto in Section 7(a)
hereof.

     "Restricted Security" means any Security or share of Common Stock issued or
issuable upon conversion thereof except any such Security or share of Common
Stock that (i) has been effectively registered under the Securities Act and sold
in a manner contemplated by the Shelf Registration Statement, (ii) has been
transferred in compliance with Rule 144 under the Securities Act (or any
successor provision thereto) or is transferable pursuant to paragraph (k) of
such Rule 144 (or any successor provision thereto), (iii) such Security or share
of Common Stock ceases to be outstanding (whether as a result of redemption,
repurchase, cancellation or conversion) or (iv) has otherwise been transferred
and a new Security or share of Common Stock not subject to transfer restrictions
under the Securities Act has been delivered by or on behalf of the Company in
accordance with the Indenture.

     "Rules and Regulations" means the published rules and regulations of the
Commission promulgated under the Securities Act or the Exchange Act, as in
effect at any relevant time.

     "Securities Act" means the United States Securities Act of 1933, as
amended.

     "Shelf Registration" means a registration effected pursuant to Section 2
hereof.

     "Shelf Registration Statement" means a "shelf" registration statement filed
under the Securities Act providing for the registration of, and the sale on a
continuous or delayed basis by the Holders of, all of the Registrable Securities
pursuant to Rule 415 under the Securities Act and/or any similar rule that may
be adopted by the Commission, filed by the Company pursuant to the provisions of
Section 2 of this Agreement, including the Prospectus contained therein, any
amendments and supplements to such registration statement, including
post-effective amendments, and all exhibits and all material incorporated by
reference in such registration statement.

     "Trust Indenture Act" means the Trust Indenture Act of 1939, or any
successor thereto, and the rules, regulations and forms promulgated thereunder,
as the same shall be amended from time to time.

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     The term "underwriter" means any underwriter of Registrable Securities in
connection with an offering thereof under a Shelf Registration Statement.

     (b)  Wherever there is a reference in this Agreement to a percentage of the
"principal amount" of Registrable Securities or to a percentage of Registrable
Securities, Common Stock shall be treated as representing the principal amount
of Securities that was surrendered for conversion or exchange in order to
receive such number of shares of Common Stock.

     2.   Shelf Registration.

     (a)  The Company shall, no later than 90 calendar days following the
Closing Date, file with the Commission a Shelf Registration Statement relating
to the offer and sale of the Registrable Securities by the Holders from time to
time in accordance with the methods of distribution elected by such Holders and
set forth in such Shelf Registration Statement and, thereafter, shall use its
best efforts to cause such Shelf Registration Statement to be declared effective
under the Securities Act no later than 210 calendar days following the Closing
Date; provided, however, that the Company may, upon written notice to all
Holders, postpone having the Shelf Registration Statement declared effective for
a reasonable period not to exceed 90 days if the Company possesses material
non-public information, the disclosure of which would have a material adverse
effect on the Company and its subsidiaries taken as a whole; provided, further,
however, that no Holder shall be entitled to be named as a selling
securityholder in the Shelf Registration Statement or to use the Prospectus
forming a part thereof for resales of Registrable Securities unless such Holder
is an Electing Holder.

     (b)  The Company shall use its best efforts:

          (i)     to keep the Shelf Registration Statement continuously
     effective under the Securities Act in order to permit the Prospectus
     forming a part thereof to be usable by Holders until the earliest of (1)
     the sale of all Registrable Securities registered under the Shelf
     Registration Statement; (2) the expiration of the period referred to in
     Rule 144(k) of the Securities with respect to all Registrable Securities
     held by Persons that are not Affiliates of the Company; (3) all the
     Registrable Securities have ceased to be outstanding (whether as a result
     of redemption, repurchase and cancellation, conversion or otherwise) and
     (4) two years from the date (the "Effective Date") such Shelf Registration
     Statement is declared effective (such period being referred to herein as
     the "Effectiveness Period");

          (ii)    after the Effective Time of the Shelf Registration Statement,
     promptly upon the request of any Holder of Registrable Securities that is
     not then an Electing Holder, to take any action reasonably necessary to
     enable such Holder to use the Prospectus forming a part thereof for resales
     of Registrable Securities, including, without limitation, any action
     necessary to identify such Holder as a selling securityholder in the Shelf
     Registration Statement; provided, however, that nothing in this
     subparagraph shall relieve such Holder of the obligation to return a
     completed and signed Notice and Questionnaire to the Company in accordance
     with Section 3(a)(ii) hereof; and

          (iii)   if at any time the Securities, pursuant to Article XII of the
     Indenture, are convertible into securities other than Common Stock, to
     cause, or to cause any successor under the Indenture to cause, such
     securities to be included in the Shelf

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     Registration Statement no later than the date on which the Securities may
     then be convertible into such securities.

The Company shall be deemed not to have used its best efforts to keep the Shelf
Registration Statement effective during the requisite period if the Company
voluntarily takes any action that would result in Holders of Registrable
Securities covered thereby not being able to offer and sell any of such
Registrable Securities during that period, unless such action is (A) required by
applicable law and the Company thereafter promptly complies with the
requirements of paragraph 3(j) below or (B) permitted pursuant to Section 2(c)
below.

     (c)  The Company may suspend the use of the Prospectus for a period not to
exceed 30 days in any 90-day period or an aggregate of 90 days in any 12-month
period if the Board of Directors of the Company shall have determined in good
faith that because of valid business reasons (not including avoidance of the
Company's obligations hereunder), including the acquisition or divestiture of
assets, pending corporate developments and similar events, it is in the best
interests of the Company to suspend such use, and prior to suspending such use
the Company provides the Holders with written notice of such suspension.

     3.   Registration Procedures. In connection with the Shelf Registration
Statement, the following provisions shall apply:

     (a)  (i) Not less than 30 calendar days prior to the Effective Time of
the Shelf Registration Statement, the Company shall mail the Notice and
Questionnaire to the Holders of Registrable Securities. No Holder shall be
entitled to be named as a selling securityholder in the Shelf Registration
Statement as of the Effective Time, and no Holder shall be entitled to use the
Prospectus forming a part thereof for resales of Registrable Securities at any
time, unless such Holder has returned a completed and signed Notice and
Questionnaire to the Company by the deadline for response set forth therein;
provided, however, Holders of Registrable Securities shall have at least 28
calendar days from the date on which the Notice and Questionnaire is first
mailed to such Holders to return a completed and signed Notice and Questionnaire
to the Company.

          (ii)    After the Effective Time of the Shelf Registration Statement,
     the Company shall, upon the request of any Holder of Registrable Securities
     that is not then an Electing Holder, promptly send a Notice and
     Questionnaire to such Holder. The Company shall not be required to take any
     action to name such Holder as a selling securityholder in the Shelf
     Registration Statement or to enable such Holder to use the Prospectus
     forming a part thereof for resales of Registrable Securities until such
     Holder has returned a completed and signed Notice and Questionnaire to the
     Company.

          (iii)   The term "Electing Holder" shall mean any Holder of
     Registrable Securities that has returned a completed and signed Notice and
     Questionnaire to the Company in accordance with Section 3(a)(i) or 3(a)(ii)
     hereof.

     (b)  The Company shall furnish to each Electing Holder, prior to the
Effective Time, a copy of the Shelf Registration Statement initially filed with
the Commission, and shall furnish to such Holders, prior to the filing thereof
with the Commission, copies of each amendment thereto and each amendment or
supplement, if any, to the Prospectus included therein, and shall use its best
efforts to reflect in each such document, at the Effective Time or when so filed
with the

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Commission, as the case may be, such comments as such Holders and their
respective counsel reasonably may propose.

     (c)  The Company shall promptly take such action as may be necessary so
that (i) each of the Shelf Registration Statement and any amendment thereto and
the Prospectus forming a part thereof and any amendment or supplement thereto
(and each report or other document incorporated therein by reference in each
case) complies in all material respects with the Securities Act and the Exchange
Act and the respective rules and regulations thereunder, (ii) each of the Shelf
Registration Statement and any amendment thereto does not, when it becomes
effective, contain an untrue statement of a material fact or omit to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading and (iii) each of the Prospectus forming a part of the
Shelf Registration Statement, and any amendment or supplement to such
Prospectus, does not at any time during the Effectiveness Period include an
untrue statement of a material fact or omit to state a material fact necessary
in order to make the statements therein, in the light of the circumstances under
which they were made, not misleading.

     (d)  The Company shall promptly advise each Electing Holder, and shall
confirm such advice in writing if so requested by any such Electing Holder:

          (i)     when a Shelf Registration Statement and any amendment thereto
     has been filed with the Commission and when a Shelf Registration Statement
     or any post-effective amendment thereto has become effective, in each case
     by making a public announcement thereof by release made directly or
     indirectly to Reuters Economic Services and Bloomberg Business News;

          (ii)    of any request by the Commission for amendments or supplements
     to the Shelf Registration Statement or the Prospectus included therein or
     for additional information;

          (iii)   of the issuance by the Commission of any stop order suspending
     the effectiveness of the Shelf Registration Statement or the initiation of
     any proceedings for such purpose;

          (iv)    of the receipt by the Company of any notification with respect
     to the suspension of the qualification of the securities included in the
     Shelf Registration Statement for sale in any jurisdiction or the initiation
     of any proceeding for such purpose; and

          (v)     of the occurrence of any event or the existence of any state
     of facts that requires the making of any changes in the Shelf Registration
     Statement or the Prospectus included therein so that, as of such date, such
     Shelf Registration Statement and Prospectus do not contain an untrue
     statement of a material fact and do not omit to state a material fact
     required to be stated therein or necessary to make the statements therein
     (in the case of the Prospectus, in light of the circumstances under which
     they were made) not misleading (which advice shall be accompanied by an
     instruction to such Holders to suspend the use of the Prospectus until the
     requisite changes have been made).

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     (e)  The Company shall use its best efforts to prevent the issuance, and if
issued to obtain the withdrawal at the earliest possible time, of any order
suspending the effectiveness of the Shelf Registration Statement.

     (f)  The Company shall furnish to each Electing Holder, without charge, at
least one copy of the Shelf Registration Statement and all post-effective
amendments thereto, including financial statements and schedules, and, if such
Electing Holder so requests in writing, all reports, other documents and
exhibits that are filed with or incorporated by reference in the Shelf
Registration Statement.

     (g)  The Company shall, during the Effectiveness Period, deliver to each
Electing Holder, without charge, as many copies of the Prospectus (including
each preliminary Prospectus) included in the Shelf Registration Statement and
any amendment or supplement thereto as such Electing Holder may reasonably
request; and the Company consents (except during the periods specified in
Section 2(c) above or during the continuance of any event or the existence of
any state of facts described in Section 3(d)(v) above) to the use of the
Prospectus and any amendment or supplement thereto by each of the Electing
Holders in connection with the offering and sale of the Registrable Securities
covered by the Prospectus and any amendment or supplement thereto during the
Effectiveness Period.

     (h)  Prior to any offering of Registrable Securities pursuant to the Shelf
Registration Statement, the Company shall (i) register or qualify or cooperate
with the Electing Holders and their respective counsel in connection with the
registration or qualification of such Registrable Securities for offer and sale
under the securities or "blue sky" laws of such jurisdictions within the United
States as any Electing Holder may reasonably request, (ii) keep such
registrations or qualifications in effect and comply with such laws so as to
permit the continuance of offers and sales in such jurisdictions for so long as
may be necessary to enable any Electing Holder or underwriter, if any, to
complete its distribution of Registrable Securities pursuant to the Shelf
Registration Statement, and (iii) take any and all other actions necessary or
advisable to enable the disposition in such jurisdictions of such Registrable
Securities; provided, however, that in no event shall the Company be obligated
to (A) qualify as a foreign corporation or as a dealer in securities in any
jurisdiction where it would not otherwise be required to so qualify but for this
Section 3(h) or (B) file any general consent to service of process in any
jurisdiction where it is not as of the date hereof so subject.

     (i)  Unless any Registrable Securities shall be in book-entry only form,
the Company shall cooperate with the Electing Holders to facilitate the timely
preparation and delivery of certificates representing Registrable Securities to
be sold pursuant to the Shelf Registration Statement, which certificates, if so
required by any securities exchange upon which any Registrable Securities are
listed, shall be penned, lithographed or engraved, or produced by any
combination of such methods, on steel engraved borders, and which certificates
shall be free of any restrictive legends and in such permitted denominations and
registered in such names as Electing Holders may request in connection with the
sale of Registrable Securities pursuant to the Shelf Registration Statement.

     (j)  Upon the occurrence of any event or the existence of any state of
facts contemplated by paragraph 3(d)(v) above, the Company shall promptly
prepare a post-effective amendment to any Shelf Registration Statement or an
amendment or supplement to the related Prospectus or file any other required
document so that, as thereafter delivered to purchasers of

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the Registrable Securities included therein, the Prospectus will not include an
untrue statement of a material fact or omit to state any material fact necessary
to make the statements therein, in the light of the circumstances under which
they were made, not misleading. If the Company notifies the Electing Holders of
the occurrence of any event or the existence of any state of facts contemplated
by paragraph 3(d)(v) above, the Electing Holder shall suspend the use of the
Prospectus until the requisite changes to the Prospectus have been made.

     (k)  Not later than the Effective Time of the Shelf Registration Statement,
the Company shall provide a CUSIP number for the Registrable Securities that are
debt securities.

     (l)  The Company shall use its best efforts to comply with all applicable
Rules and Regulations, and to make generally available to its securityholders as
soon as practicable, but in any event not later than eighteen months after (i)
the effective date (as defined in Rule 158(c) under the Securities Act) of the
Shelf Registration Statement, (ii) the effective date of each post-effective
amendment to the Shelf Registration Statement, and (iii) the date of each filing
by the Company with the Commission of an Annual Report on Form 10-K that is
incorporated by reference in the Shelf Registration Statement, an earning
statement of the Company and its subsidiaries complying with Section 11(a) of
the Securities Act and the rules and regulations of the Commission thereunder
(including, at the option of the Company, Rule 158).

     (m)  Not later than the Effective Time of the Shelf Registration Statement,
the Company shall cause the Indenture to be qualified under the Trust Indenture
Act; in connection with such qualification, the Company shall cooperate with the
Trustee under the Indenture and the Holders (as defined in the Indenture) to
effect such changes to the Indenture as may be required for such Indenture to be
so qualified in accordance with the terms of the Trust Indenture Act; and the
Company shall execute, and shall use all reasonable efforts to cause the Trustee
to execute, all documents that may be required to effect such changes and all
other forms and documents required to be filed with the Commission to enable
such Indenture to be so qualified in a timely manner. In the event that any such
amendment or modification referred to in this Section 3(m) involves the
appointment of a new trustee under the Indenture, the Company shall appoint a
new trustee thereunder pursuant to the applicable provisions of the Indenture.

     (n)  In the event of an underwritten offering conducted pursuant to Section
6 hereof, the Company shall, if requested, promptly include or incorporate in a
Prospectus supplement or post-effective amendment to the Shelf Registration
Statement such information as the Managing Underwriters reasonably agree should
be included therein and to which the Company does not reasonably object and
shall make all required filings of such Prospectus supplement or post-effective
amendment as soon as practicable after it is notified of the matters to be
included or incorporated in such Prospectus supplement or post-effective
amendment.

     (o)  The Company shall enter into such customary agreements (including an
underwriting agreement in customary form in the event of an underwritten
offering conducted pursuant to Section 6 hereof) and take all other appropriate
action in order to expedite and facilitate the registration and disposition of
the Registrable Securities, and in connection therewith, if an underwriting
agreement is entered into, cause the same to contain indemnification provisions
and procedures substantially identical to those set forth in Section 5 hereof
with respect to all parties to be indemnified pursuant to Section 5 hereof.

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     (p)  The Company shall:

          (i)(A)  make reasonably available for inspection by the Electing
     Holders, any underwriter participating in any disposition pursuant to the
     Shelf Registration Statement, and any attorney, accountant or other agent
     retained by such Electing Holders or any such underwriter all relevant
     financial and other records, pertinent corporate documents and properties
     of the Company and its subsidiaries, and (B) cause the Company's officers,
     directors and employees to supply all information reasonably requested by
     such Electing Holders or any such underwriter, attorney, accountant or
     agent in connection with the Shelf Registration Statement, in each case, as
     is customary for similar due diligence examinations; provided, however,
     that all records, information and documents that are designated in writing
     by the Company, in good faith, as confidential shall be kept confidential
     by such Electing Holders and any such underwriter, attorney, accountant or
     agent, unless such disclosure is made in connection with a court proceeding
     or required by law, or such records, information or documents become
     available to the public generally or through a third party without an
     accompanying obligation of confidentiality; and provided further that, if
     the foregoing inspection and information gathering would otherwise disrupt
     the Company's conduct of its business, such inspection and information
     gathering shall, to the greatest extent possible, be coordinated on behalf
     of the Electing Holders and the other parties entitled thereto by one
     counsel designated by and on behalf of the Electing Holders and other
     parties;

          (ii)    in connection with any underwritten offering conducted
     pursuant to Section 6 hereof, make such representations and warranties to
     the Electing Holders participating in such underwritten offering and to the
     Managing Underwriters, in form, substance and scope as are customarily made
     by the Company to underwriters in primary underwritten offerings of equity
     and convertible debt securities and covering matters including, but not
     limited to, those set forth in the Purchase Agreement;

          (iii)   in connection with any underwritten offering conducted
     pursuant to Section 6 hereof, obtain opinions of counsel to the Company
     (which counsel and opinions (in form, scope and substance) shall be
     reasonably satisfactory to the Managing Underwriters) addressed to each
     Electing Holder participating in such underwritten offering and the
     underwriters, covering such matters as are customarily covered in opinions
     requested in primary underwritten offerings of equity and convertible debt
     securities and such other matters as may be reasonably requested by such
     Electing Holders and underwriters (it being agreed that the matters to be
     covered by such opinions shall include, without limitation, as of the date
     of the opinion and as of the Effective Time of the Shelf Registration
     Statement or most recent post-effective amendment thereto, as the case may
     be, the absence from the Shelf Registration Statement and the Prospectus,
     including the documents incorporated by reference therein, of an untrue
     statement of a material fact or the omission of a material fact required to
     be stated therein or necessary to make the statements therein not
     misleading;

          (iv)    in connection with any underwritten offering conducted
     pursuant to Section 6 hereof, obtain "cold comfort" letters and updates
     thereof from the independent public accountants of the Company (and, if
     necessary, from the independent public accountants of any subsidiary of the
     Company or of any business acquired by the

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     Company for which financial statements and financial data are, or are
     required to be, included in the Shelf Registration Statement), addressed to
     each Electing Holder participating in such underwritten offering (if such
     Electing Holder has provided such letter, representations or documentation,
     if any, required for such cold comfort letter to be so addressed) and the
     underwriters, in customary form and covering matters of the type
     customarily covered in "cold comfort" letters in connection with primary
     underwritten offerings;

          (v)     in connection with any underwritten offering conducted
     pursuant to Section 6 hereof, deliver such documents and certificates as
     may be reasonably requested by any Electing Holders participating in such
     underwritten offering and the Managing Underwriters, if any, including,
     without limitation, certificates to evidence compliance with Section 3(j)
     hereof and with any conditions contained in the underwriting agreement or
     other agreements entered into by the Company.

     (q)  The Company will use its best efforts to cause the Common Stock
issuable upon conversion of the Securities to be listed for quotation on the
Nasdaq National Market System or other stock exchange or trading system on which
the Common Stock primarily trades on or prior to the Effective Time of the Shelf
Registration Statement hereunder.

     (r)  In the event that any broker-dealer registered under the Exchange Act
shall be an "affiliate" (as defined in Rule 2720(b)(1) of the NASD Rules (or any
successor provision thereto)) of the Company or has a "conflict of interest" (as
defined in Rule 2720(b)(7) of the NASD Rules (or any successor provision
thereto)) and such broker-dealer shall underwrite, participate as a member of an
underwriting syndicate or selling group or assist in the distribution of any
Registrable Securities covered by the Shelf Registration Statement, whether as a
Holder of such Registrable Securities or as an underwriter, a placement or sales
agent or a broker or dealer in respect thereof, or otherwise, the Company shall
assist such broker-dealer in complying with the requirements of the NASD Rules,
including, without limitation, by (A) engaging a "qualified independent
underwriter" (as defined in Rule 2720(b)(15) of the NASD Rules (or any successor
provision thereto)) to participate in the preparation of the registration
statement relating to such Registrable Securities, to exercise usual standards
of due diligence in respect thereto and to recommend the public offering price
of such Registrable Securities, (B) indemnifying such qualified independent
underwriter to the extent of the indemnification of underwriters provided in
Section 5 hereof, and (C) providing such information to such broker-dealer as
may be required in order for such broker-dealer to comply with the requirements
of the NASD Rules.

     (s)  The Company shall use its best efforts to take all other steps
necessary to effect the registration, offering and sale of the Registrable
Securities covered by the Shelf Registration Statement contemplated hereby.

     4.   Registration Expenses. Except as otherwise provided in Section 3, the
Company shall bear all fees and expenses incurred in connection with the
performance of its obligations under Sections 2, 3 and 6 hereof and shall bear
or reimburse the Electing Holders for the reasonable fees and disbursements of a
single counsel selected by a plurality of all Electing Holders who own an
aggregate of not less than 25% of the Registrable Securities covered by the
Shelf Registration Statement to act as counsel therefore in connection
therewith. Each Electing Holder shall pay all underwriting discounts and
commissions and transfer and income

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taxes, if any, relating to the sale or disposition of such Electing Holder's
Registrable Securities pursuant to the Shelf Registration Statement.

     5.   Indemnification and Contribution.

     (a)  Indemnification by the Company. Upon the registration of the
Registrable Securities pursuant to Section 2 hereof, the Company shall indemnify
and hold harmless each Electing Holder and each underwriter, dealer, selling
agent or other securities professional, if any, which facilitates the
disposition of Registrable Securities, and each of their respective officers and
directors and each person who controls such Electing Holder, underwriter,
dealer, selling agent or other securities professional within the meaning of
Section 15 of the Securities Act or Section 20 of the Exchange Act (each such
person being sometimes referred to as an "Indemnified Person") against any
losses, claims, damages or liabilities, joint or several, to which such
Indemnified Person may become subject under the Securities Act or otherwise,
insofar as such losses, claims, damages or liabilities (or actions in respect
thereof) arise out of or are based upon an untrue statement or alleged untrue
statement of a material fact contained in any Shelf Registration Statement under
which such Registrable Securities are to be registered under the Securities Act,
or any Prospectus contained therein or furnished by the Company to any
Indemnified Person, or any amendment or supplement thereto, or arise out of or
are based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, and the Company hereby agrees to reimburse such Indemnified Person
for any legal or other expenses reasonably incurred by it in connection with
investigating or defending any such action or claim as such expenses are
incurred; provided, however, that the Company shall not be liable to any such
Indemnified Person in any such case to the extent that any such loss, claim,
damage or liability arises out of or is based upon an untrue statement or
alleged untrue statement or omission or alleged omission made in such Shelf
Registration Statement or Prospectus, or amendment or supplement, in reliance
upon and in conformity with written information furnished to the Company by such
Indemnified Person expressly for use therein.

     (b)  Indemnification by the Electing Holders and any Agents and
Underwriters. Each Electing Holder agrees, as a consequence of the inclusion of
any of such Electing Holder's Registrable Securities in such Shelf Registration
Statement, and each underwriter, dealer, selling agent or other securities
professional, if any, which facilitates the disposition of Registrable
Securities shall agree, as a consequence of facilitating such disposition of
Registrable Securities, severally and not jointly, to (i) indemnify and hold
harmless the Company, its directors, officers who sign any Shelf Registration
Statement and each person, if any, who controls the Company within the meaning
of either Section 15 of the Securities Act or Section 20 of the Exchange Act,
against any losses, claims, damages or liabilities to which the Company or such
other persons may become subject, under the Securities Act or otherwise, insofar
as such losses, claims, damages or liabilities (or actions in respect thereof)
arise out of or are based upon an untrue statement or alleged untrue statement
of a material fact contained in such Shelf Registration Statement or Prospectus,
or any amendment or supplement, or arise out of or are based upon the omission
or alleged omission to state therein a material fact required to be stated
therein or necessary to make the statements therein not misleading, in each case
to the extent, but only to the extent, that such untrue statement or alleged
untrue statement or omission or alleged omission was made in reliance upon and
in conformity with written information furnished to the Company by such Electing
Holder, underwriter, dealer,

                                       11

<PAGE>

selling agent or other securities professional expressly for use therein, and
(ii) reimburse the Company for any legal or other expenses reasonably incurred
by the Company in connection with investigating or defending any such action or
claim as such expenses are incurred.

     (c)  Notices of Claims, Etc. Promptly after receipt by an indemnified party
under subsection (a) or (b) above of notice of the commencement of any action,
such indemnified party shall, if a claim in respect thereof is to be made
against an indemnifying party under this Section 5, notify such indemnifying
party in writing of the commencement thereof; but the omission so to notify the
indemnifying party shall not relieve it from any liability which it may have to
any indemnified party otherwise than under the indemnification provisions of or
contemplated by subsection (a) or (b) above. In case any such action shall be
brought against any indemnified party and it shall notify an indemnifying party
of the commencement thereof, such indemnifying party shall be entitled to
participate therein and, to the extent that it shall wish, jointly with any
other indemnifying party similarly notified, to assume the defense thereof, with
counsel satisfactory to such indemnified party (who shall not, except with the
consent of the indemnified party, be counsel to the indemnifying party), and,
after notice from the indemnifying party to such indemnified party of its
election so to assume the defense thereof, such indemnifying party shall not be
liable to such indemnified party under this Section 5 for any legal expenses of
other counsel or any other expenses, in each case subsequently incurred by such
indemnified party, in connection with the defense thereof other than reasonable
costs of investigation. No indemnifying party shall, without the written consent
of the indemnified party, effect the settlement or compromise of, or consent to
the entry of any judgment with respect to, any pending or threatened action or
claim in respect of which indemnification or contribution may be sought
hereunder (whether or not the indemnified party is an actual or potential party
to such action or claim) unless such settlement, compromise or judgment (i)
includes an unconditional release of the indemnified party from all liability
arising out of such action or claim and (ii) does not include a statement as to,
or an admission of, fault, culpability or a failure to act, by or on behalf of
any indemnified party.

     (d)  Contribution. If the indemnification provided for in this Section 5 is
unavailable to or insufficient to hold harmless an indemnified party under
subsection (a) or (b) above in respect of any losses, claims, damages or
liabilities (or actions in respect thereof) referred to therein, then each
indemnifying party shall contribute to the amount paid or payable by such
indemnified party as a result of such losses, claims, damages or liabilities (or
actions in respect thereof) in such proportion as is appropriate to reflect the
relative fault of the indemnifying party and the indemnified party in connection
with the statements or omissions which resulted in such losses, claims, damages
or liabilities (or actions in respect thereof), as well as any other relevant
equitable considerations. The relative fault of such indemnifying party and
indemnified party shall be determined by reference to, among other things,
whether the untrue or alleged untrue statement of a material fact or omission or
alleged omission to state a material fact relates to information supplied by
such indemnifying party or by such indemnified party, and the parties' relative
intent, knowledge, access to information and opportunity to correct or prevent
such statement or omission. The parties hereto agree that it would not be just
and equitable if contribution pursuant to this Section 5(d) were determined by
pro rata allocation (even if the Electing Holders or any underwriters, dealers,
selling agents or other securities professionals or all of them were treated as
one entity for such purpose) or by any other method of allocation which does not
take account of the equitable considerations referred to in this Section 5(d).
The amount paid or payable by an indemnified party as a result of the losses,
claims, damages or

                                       12

<PAGE>

liabilities (or actions in respect thereof) referred to above shall be deemed to
include any legal or other fees or expenses reasonably incurred by such
indemnified party in connection with investigating or defending any such action
or claim. No person guilty of fraudulent misrepresentation (within the meaning
of Section 11(f) of the Securities Act) shall be entitled to contribution from
any person who was not guilty of such fraudulent misrepresentation. The
obligations of the Electing Holders and any underwriters, dealers, selling
agents or other securities professionals in this Section 5(d) to contribute
shall be several in proportion to the percentage of principal amount of
Registrable Securities registered or underwritten, as the case may be, by them
and not joint.

     (e)  Notwithstanding any other provision of this Section 5, in no event
will any (i) Electing Holder be required to undertake liability to any person
under this Section 5 for any amounts in excess of the dollar amount of the
proceeds to be received by such Holder from the sale of such Holder's
Registrable Securities (after deducting any fees, discounts and commissions
applicable thereto) pursuant to any Shelf Registration Statement under which
such Registrable Securities are to be registered under the Securities Act and
(ii) underwriter, dealer, selling agent or other securities professional be
required to undertake liability to any person hereunder for any amounts in
excess of the discount, commission or other compensation payable to such
underwriter, dealer, selling agent or other securities professional with respect
to the Registrable Securities underwritten by it and distributed to the public.

     (f)  The obligations of the Company under this Section 5 shall be in
addition to any liability which the Company may otherwise have to any
Indemnified Person and the obligations of any Indemnified Person under this
Section 5 shall be in addition to any liability which such Indemnified Person
may otherwise have to the Company. The remedies provided in this Section 5 are
not exclusive and shall not limit any rights or remedies which may otherwise be
available to an indemnified party at law or in equity.

     6.   Underwritten Offering. Any Holder of Registrable Securities who
desires to do so may sell Registrable Securities (in whole or in part) in an
underwritten offering; provided that (i) the Electing Holders of at least
33-1/3% in aggregate principal amount of the Registrable Securities then covered
by the Shelf Registration Statement shall request such an offering and (ii) at
least such aggregate principal amount of such Registrable Securities shall be
included in such offering; and provided further that the Company shall not be
obligated to cooperate with more than one underwritten offering during the
Effectiveness Period. Upon receipt of such a request, the Company shall provide
all Holders of Registrable Securities written notice of the request, which
notice shall inform such Holders that they have the opportunity to participate
in the offering. In any such underwritten offering, the investment banker or
bankers and manager or managers that will administer the offering will be
selected by, and the underwriting arrangements with respect thereto (including
the size of the offering) will be approved by, the holders of a majority of the
Registrable Securities to be included in such offering; provided, however, that
such investment bankers and managers and underwriting arrangements must be
reasonably satisfactory to the Company. No Holder may participate in any
underwritten offering contemplated hereby unless (a) such Holder agrees to sell
such Holder's Registrable Securities to be included in the underwritten offering
in accordance with any approved underwriting arrangements, (b) such Holder
completes and executes all reasonable questionnaires, powers of attorney,
indemnities, underwriting agreements, lock-up letters and other documents
required under the terms of such approved underwriting arrangements, and (c) if
such Holder is not then

                                       13

<PAGE>

an Electing Holder, such Holder returns a completed and signed Notice and
Questionnaire to the Company in accordance with Section 3(a)(ii) hereof within a
reasonable amount of time before such underwritten offering. The Holders
participating in any underwritten offering shall be responsible for any
underwriting discounts and commissions and fees and, subject to Section 4
hereof, expenses of their own counsel. The Company shall pay all expenses
customarily borne by issuers in an underwritten offering, including but not
limited to filing fees, the fees and disbursements of its counsel and
independent public accountants and any printing expenses incurred in connection
with such underwritten offering. Notwithstanding the foregoing or the provisions
of Section 3(n) hereof, upon receipt of a request from the Managing Underwriter
or a representative of holders of a majority of the Registrable Securities to be
included in an underwritten offering to prepare and file an amendment or
supplement to the Shelf Registration Statement and Prospectus in connection with
an underwritten offering, the Company may delay the filing of any such amendment
or supplement for up to 90 days if the Board of Directors of the Company shall
have determined in good faith that the Company has a bona fide business reason
for such delay.

     7.   Liquidated Damages.

     (a)  Notwithstanding any postponement of effectiveness permitted by Section
2(a) hereof, if (i) on or prior to the 90th day following the Closing Date, a
Shelf Registration Statement has not been filed with the Commission or (ii) on
or prior to the 210th day following the Closing Date, such Shelf Registration
Statement is not declared effective by the Commission (each, a "Registration
Default"), the Company shall be required to pay liquidated damages ("Liquidated
Damages"), from and including the day following such Registration Default until
such Shelf Registration Statement is either so filed or so filed and
subsequently declared effective, as applicable, at a rate per annum equal to an
additional one-quarter of one percent (0.25%) of the principal amount of
Registrable Securities, to and including the 90th day following such
Registration Default and one-half of one percent (0.50%) thereof from and after
the 91st day following such Registration Default.

     (b)  In the event that (i) the Shelf Registration Statement ceases to be
effective, (ii) the Company suspends the use of the Prospectus pursuant to
Section 2(c) or 3(j) hereof, (iii) the Holders are not authorized to use the
Prospectus pursuant to Section 3(g) hereto or (iv) the Holders are otherwise
prevented or restricted by the Company from effecting sales pursuant to the
Shelf Registration Statement (an "Effective Failure") for more than 30 days,
whether or not consecutive, in any 90-day period, or for more than 90 days,
whether or not consecutive, during any 12-month period, then the Company shall
pay Liquidated Damages at a rate per annum equal to an additional one-half of
one percent (0.50%) of the principal amount of Registrable Securities from the
31st day of the applicable 90-day period or the 91st day of the applicable
12-month period, as the case may be, that any such Effective Failure has existed
until the earlier of (1) the time the Holders of Registrable Securities are
again able to make sales under the Shelf Registration Statement or (2) the
expiration of the Effectiveness Period.

     (c)  Any amounts to be paid as Liquidated Damages pursuant to paragraphs
(a) or (b) of this Section 7 shall be paid in cash semi-annually in arrears,
with the first semi-annual payment due on the first Interest Payment Date (as
defined in the Indenture), as applicable, following the date of such
Registration Default or Effective Failure, as applicable. Such Liquidated
Damages will accrue (1) in respect of the Securities at the rates set forth in
paragraphs (a) or (b) of this Section 7, as applicable, on the principal amount
of the Securities

                                       14

<PAGE>

and (2) in respect of the Common Stock issued upon conversion of the Securities,
at the rates set forth in paragraphs (a) or (b) of this Section 7, as
applicable, applied to the Conversion Price (as defined in the Indenture) at
that time.

     (d)  Except as provided in Section 8(b) hereof, the Liquidated Damages as
set forth in this Section 7 shall be the exclusive monetary remedy available to
the Holders of Registrable Securities for such Registration Default or Effective
Failure. In no event shall the Company be required to pay Liquidated Damages in
excess of the applicable maximum rate per annum of one-half of one percent
(0.50%) set forth above, regardless of whether one or multiple Registration
Defaults or Effective Failures exist.

     8.   Miscellaneous.

     (a)  Other Registration Rights. The Company may grant registration rights
that would permit any person that is a third party the right to piggy-back on
any Shelf Registration Statement, provided that if the Managing Underwriter of
any underwritten offering conducted pursuant to Section 6 hereof notifies the
Company and the Electing Holders that the total amount of securities which the
Electing Holders and the holders of such piggy-back rights intend to include in
any Shelf Registration Statement is so large as to materially threaten the
success of such offering (including the price at which such securities can be
sold), then the amount, number or kind of securities to be offered for the
account of holders of such piggy-back rights will be reduced to the extent
necessary to reduce the total amount of securities to be included in such
offering to the amount, number and kind recommended by the Managing Underwriter
prior to any reduction in the amount of Registrable Securities to be included in
such Shelf Registration Statement.

     (b)  Specific Performance. The parties hereto acknowledge that there would
be no adequate remedy at law if the Company fails to perform any of its
obligations hereunder and that the Purchasers and the Holders from time to time
may be irreparably harmed by any such failure, and accordingly agree that the
Purchasers and such Holders, in addition to any other remedy to which they may
be entitled at law or in equity and without limiting the remedies available to
the Electing Holders under Section 7 hereof, shall be entitled to compel
specific performance of the obligations of the Company under this Registration
Rights Agreement in accordance with the terms and conditions of this
Registration Rights Agreement, in any court of the United States or any State
thereof having jurisdiction.

     (c)  Amendments and Waivers. This Agreement, including this Section 8(c),
may be amended, and waivers or consents to departures from the provisions hereof
may be given, only by a written instrument duly executed by the Company and the
holders of a majority in aggregate principal amount of Registrable Securities
then outstanding. Each Holder of Registrable Securities outstanding at the time
of any such amendment, waiver or consent or thereafter shall be bound by any
amendment, waiver or consent effected pursuant to this Section 8(c), whether or
not any notice, writing or marking indicating such amendment, waiver or consent
appears on the Registrable Securities or is delivered to such Holder.

     (d)  Notices. All notices and other communications provided for or
permitted hereunder shall be given as provided in the Indenture.

                                       15

<PAGE>

     (e)  Parties in Interest. The parties to this Agreement intend that all
Holders of Registrable Securities shall be entitled to receive the benefits of
this Agreement and that any Electing Holder shall be bound by the terms and
provisions of this Agreement by reason of such election with respect to the
Registrable Securities which are included in a Shelf Registration Statement. All
the terms and provisions of this Agreement shall be binding upon, shall inure to
the benefit of and shall be enforceable by the respective successors and assigns
of the parties hereto and any Holder from time to time of the Registrable
Securities to the aforesaid extent. In the event that any transferee of any
Holder of Registrable Securities shall acquire Registrable Securities, in any
manner, whether by gift, bequest, purchase, operation of law or otherwise, such
transferee shall, without any further writing or action of any kind, be entitled
to receive the benefits of and, if an Electing Holder, be conclusively deemed to
have agreed to be bound by and to perform all of the terms and provisions of
this Agreement to the aforesaid extent.

     (f)  Counterparts. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

     (g)  Headings. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

     (h)  Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of New York.

     (i)  Severability. In the event that any one or more of the provisions
contained herein, or the application thereof in any circumstances, is held
invalid, illegal or unenforceable in any respect for any reason, the validity,
legality and enforceability of any such provision in every other respect and of
the remaining provisions hereof shall not be in any way impaired or affected
thereby, it being intended that all of the rights and privileges of the parties
hereto shall be enforceable to the fullest extent permitted by law.

     (j)  Survival. The respective indemnities, agreements, representations,
warranties and other provisions set forth in this Agreement or made pursuant
hereto shall remain in full force and effect, regardless of any investigation
(or any statement as to the results thereof) made by or on behalf of any
Electing Holder, any director, officer or partner of such Holder, any agent or
underwriter, any director, officer or partner of such agent or underwriter, or
any controlling person of any of the foregoing, and shall survive the transfer
and registration of the Registrable Securities of such Holder.

                                       16

<PAGE>

     Please confirm that the foregoing correctly sets forth the agreement
between the Company and you.

                                               Very truly yours,

                                               Medarex, Inc.


                                               By: _____________________________
                                                   Name:
                                                   Title:

Accepted as of the date hereof:

Goldman, Sachs & Co.
UBS Securities LLC
J.P. Morgan Securities Inc.


By: ____________________________________
           (Goldman, Sachs & Co.)

    On behalf of each of the Purchasers.

                                       17

<PAGE>

                                                                      Appendix A

                                  MEDAREX, INC.

                         INSTRUCTION TO DTC PARTICIPANTS

                                (Date of Mailing)

                     URGENT - IMMEDIATE ATTENTION REQUESTED

                          DEADLINE FOR RESPONSE: [DATE]

          The Depository Trust Company ("DTC") has identified you as a DTC
Participant through which beneficial interests in the Medarex, Inc. (the
"Company") 4.25% Convertible Senior Notes due 2008 (the "Securities") are held.

          The Company is in the process of registering the Securities under the
Securities Act of 1933 for resale by the beneficial owners thereof. In order to
have their Securities included in the registration statement, beneficial owners
must complete and return the enclosed Notice of Registration Statement and
Selling Securityholder Questionnaire.

          It is important that beneficial owners of the Securities receive a
copy of the enclosed materials as soon as possible as their rights to have the
Securities included in the registration statement depend upon their returning
the Notice and Questionnaire by [Deadline for response]. Please forward a copy
of the enclosed documents to each beneficial owner that holds interests in the
Securities through you. If you require more copies of the enclosed materials or
have any questions pertaining to this matter, please contact [Name, address and
telephone number of contact at the Issuer].

                                       18

<PAGE>


                                  MEDAREX, INC.

                        NOTICE OF REGISTRATION STATEMENT
                                       and
                      SELLING SECURITYHOLDER QUESTIONNAIRE

                                      ,2003

          Medarex, Inc. (the "Company") has filed with the United States
Securities and Exchange Commission (the "Commission") a registration statement
on Form S-3 (the "Shelf Registration Statement") for the registration and resale
under Rule 415 of the United States Securities Act of 1933, as amended (the
"Securities Act"), of the Company's 4.25% Convertible Senior Notes due 2010 (the
"Securities") and the shares of common stock, par value $.01 per share (the
"Common Stock"), issuable upon conversion thereof, in accordance with the
Registration Rights Agreement, dated as of July 23, 2003 (the "Registration
Rights Agreement"), between the Company and the purchasers named therein. A copy
of the Registration Rights Agreement is attached hereto. All capitalized terms
not otherwise defined herein shall have the meanings ascribed thereto in the
Registration Rights Agreement.

          In order to have Registrable Securities included in the Shelf
Registration Statement (or a supplement or amendment thereto), this Notice of
Registration Statement and Selling Securityholder Questionnaire ("Notice and
Questionnaire") must be completed, executed and delivered to the Company at the
address set forth herein for receipt ON OR BEFORE ____ __, 2003. Beneficial
owners of Registrable Securities who do not complete, execute and return this
Notice and Questionnaire by such date (i) will not be named as selling
securityholders in the Shelf Registration Statement and (ii) may not use the
Prospectus forming a part thereof for resales of Registrable Securities.

          Certain legal consequences arise from being named as a selling
securityholder in the Shelf Registration Statement and related Prospectus.
Accordingly, holders and beneficial owners of Registrable Securities are advised
to consult their own securities law counsel regarding the consequences of being
named or not being named as a selling securityholder in the Shelf Registration
Statement and related Prospectus.

                                       19

<PAGE>

          The term "Registrable Securities" is defined in the Registration
Rights Agreement to mean all or any portion of the Securities issued from time
to time under the Indenture in registered form and the shares of Common Stock
issued or issuable upon conversion, repurchase or redemption of such Securities;
provided, however, that a security ceases to be a Registrable Security when it
is no longer a Restricted Security.

          The term "Restricted Security" is defined in the Registration Rights
Agreement to mean any Security or share of Common Stock issued or issuable upon
conversion thereof except any such Security or share of Common Stock which (i)
has been effectively registered under the Securities Act and sold in a manner
contemplated by the Shelf Registration Statement, (ii) has been transferred in
compliance with Rule 144 under the Securities Act (or any successor provision
thereto) or is transferable pursuant to paragraph (k) of such Rule 144 (or any
successor provision thereto), (iv) such Security or share of Common Stock ceases
to be outstanding (whether as a result of redemption, repurchase, cancellation
or conversion) or (v) has otherwise been transferred and a new Security or share
of Common Stock not subject to transfer restrictions under the Securities Act
has been delivered by or on behalf of the Company in accordance with the
Indenture.

                                    ELECTION

          The undersigned holder (the "Selling Securityholder") of Registrable
Securities hereby elects to include in the Shelf Registration Statement the
Registrable Securities beneficially owned by it and listed below in Item (3).
The undersigned, by signing and returning this Notice and Questionnaire, agrees
to be bound with respect to such Registrable Securities by the terms and
conditions of this Notice and Questionnaire and the Registration Rights
Agreement, including, without limitation, Section 5 of the Registration Rights
Agreement, as if the undersigned Selling Securityholder were an original party
thereto.

          Upon any sale of Registrable Securities pursuant to the Shelf
Registration Statement, the Selling Securityholder will be required to deliver
to the Company and the Trustee the Notice of Transfer (completed and signed) set
forth in Exhibit 1 to this Notice and Questionnaire.

          The Selling Securityholder hereby provides the following information
to the Company and represents and warrants that such information is accurate and
complete:

                                       20

<PAGE>

                                  QUESTIONNAIRE

(1)  (a)  Full legal name of Selling Securityholder:

          ______________________________________________________________________

     (b)  Full legal name of Registered Holder (if not the same as in (a) above)
          of Registrable Securities Listed in Item (3) below:

          ______________________________________________________________________

     (c)  Full legal name of DTC participant (if applicable and if not the same
          as (b) above) through which Registrable Securities listed in Item (3)
          below are held:

          ______________________________________________________________________

(2)       Address for notices to Selling Securityholder:

                           __________________________________
                           __________________________________
                           __________________________________
          Telephone:       __________________________________
          Fax:             __________________________________
          Contact Person:  __________________________________

(3)       Beneficial ownership of Securities:

          Except as set forth below in this Item (3), the undersigned Selling
          Securityholder does not beneficially own any Securities or shares of
          Common Stock issued upon conversion, repurchase or redemption of any
          Securities.

     (a)  Principal amount of Registrable Securities (as defined in the
          Registration Rights Agreement) beneficially owned: ___________________
          CUSIP No(s). of such Registrable Securities:__________________________

          ______________________________________________________________________

          Number of shares of Common Stock (if any) issued upon conversion,
          repurchase or redemption of Registrable Securities:___________________

     (b)  Principal amount of securities other than Registrable Securities
          beneficially owned:___________________________________________________

          CUSIP No(s). of such other Securities: _______________________________

          Number of shares of Common Stock (if any) issued upon conversion of
          such other Securities:________________________________________________

     (c)  Principal amount of Registrable Securities which the undersigned
          wishes to be included in the Shelf Registration Statement:____________
          __________________________________________________________

          CUSIP No(s). of such Registrable Securities to be included in the
          Shelf Registration Statement: ________________________________________

          Number of shares of Common Stock (if any) issued upon conversion of
          Registrable Securities which are to be included in the Shelf
          Registration Statement: ______________________________________________

                                       21

<PAGE>

(4)  Beneficial ownership of other securities of the Company:

     Except as set forth below in this Item (4), the undersigned Selling
     Securityholder is not the beneficial or registered owner of any shares of
     Common Stock or any other securities of the Company, other than the
     Securities and shares of Common Stock listed above in Item (3).

     State any exceptions here:

(5)  Relationships with the Company:

     Except as set forth below, neither the Selling Securityholder nor any of
     its affiliates, officers, directors or principal equity holders (5% or
     more) has held any position or office or has had any other material
     relationship with the Company (or its predecessors or affiliates) during
     the past three years.

     State any exceptions here:

(6)  Plan of Distribution:

     Except as set forth below, the undersigned Selling Securityholder intends
     to distribute the Registrable Securities listed above in Item (3) only as
     follows (if at all): Such Registrable Securities may be sold from time to
     time directly by the undersigned Selling Securityholder or, alternatively,
     through underwriters, broker-dealers or agents. Such Registrable Securities
     may be sold in one or more transactions at fixed prices, at prevailing
     market prices at the time of sale, at varying prices determined at the time
     of sale, or at negotiated prices. Such sales may be effected in
     transactions (which may involve crosses or block transactions) (i) on any
     national securities exchange or quotation service on which the Registrable
     Securities may be listed or quoted at the time of sale, (ii) in the
     over-the-counter market, (iii) in transactions otherwise than on such
     exchanges or services or in the over-the-counter market, or (iv) through
     the writing of options. In connection with sales of the Registrable
     Securities or otherwise, the Selling Securityholder may enter into hedging
     transactions with broker-dealers, which may in turn engage in short sales
     of the Registrable Securities in the course of hedging the positions they
     assume. The Selling Securityholder may also sell Registrable Securities
     short and deliver Registrable Securities to close out such short positions,
     or loan or pledge Registrable Securities to broker-dealers that in turn may
     sell such securities. The Selling Securityholder may pledge or grant
     security interest in some or all of the Registrable Securities owned by it
     and, if it defaults in the performance of its secured obligations, the
     pledgees or secured parties may offer and sell the Registrable Securities
     from time to time pursuant to the prospectus. The Selling Securityholder
     also may transfer and donate shares in other circumstances in which case
     the transferees, donees, pledgees or other successors in interest will be
     the selling security holder for purposes of the prospectus.

     State any exceptions here:

                                       22

<PAGE>

          Note: Underwritten offerings of the Registrable Securities are subject
to the limitations set forth in the Registration Rights Agreement.

          By signing below, the Selling Securityholder acknowledges that it
understands its obligation to comply, and agrees that it will comply, with the
prospectus delivery and other provisions of the Securities Act and the
Securities Exchange Act of 1934, as amended, and the rules and regulations
thereunder, particularly Regulation M.

          In the event that the Selling Securityholder transfers all or any
portion of the Registrable Securities listed in Item (3) above after the date on
which such information is provided to the Company, the Selling Securityholder
agrees to notify the transferee(s) at the time of the transfer of its rights and
obligations under this Notice and Questionnaire and the Registration Rights
Agreement.

          By signing below, the Selling Securityholder consents to the
disclosure of the information contained herein in its answers to Items (1)
through (6) above and the inclusion of such information in the Shelf
Registration Statement and related Prospectus. The Selling Securityholder
understands that such information will be relied upon by the Company in
connection with the preparation of the Shelf Registration Statement and related
Prospectus.

          In accordance with the Selling Securityholder's obligation under
Section 3(a) of the Registration Rights Agreement to provide such information as
may be required by law for inclusion in the Shelf Registration Statement, the
Selling Securityholder agrees to promptly notify the Company of any inaccuracies
or changes in the information provided herein which may occur subsequent to the
date hereof at any time while the Shelf Registration Statement remains in
effect. All notices hereunder and pursuant to the Registration Rights Agreement
shall be made in writing, by hand-delivery, first-class mail, or air courier
guaranteeing overnight delivery as follows:

     (i)  To the Company:

                                          Medarex, Inc.
                                          --------------------------------------
                                          707 State Road, #206
                                          --------------------------------------
                                          Princeton, New Jersey 08540
                                          --------------------------------------
                                          Attn: General Counsel
                                          --------------------------------------

                                          --------------------------------------








     (ii) With a copy to:

                                          Satterlee, Stephens, Burke & Burke LLP
                                          --------------------------------------
                                          230 Park Avenue, Suite 1130
                                          --------------------------------------
                                          New York, New York  10169
                                          --------------------------------------
                                          Attn: Dwight Kinsey
                                          --------------------------------------

                                          --------------------------------------

                                       23

<PAGE>

          Once this Notice and Questionnaire is executed by the Selling
Securityholder and received by the Company, the terms of this Notice and
Questionnaire, and the representations and warranties contained herein, shall be
binding on, shall inure to the benefit of and shall be enforceable by the
respective successors, heirs, personal representatives, and assigns of the
Company and the Selling Securityholder (with respect to the Registrable
Securities beneficially owned by such Selling Securityholder and listed in Item
(3) above). This Agreement shall be governed in all respects by the laws of the
State of New York.

                                       24

<PAGE>

          IN WITNESS WHEREOF, the undersigned, by authority duly given, has
caused this Notice and Questionnaire to be executed and delivered either in
person or by its duly authorized agent.

Dated: ____________________________


          ______________________________________________________________________

          Selling Securityholder
          (Print/type full legal name of beneficial owner of Registrable
          Securities)


          By: __________________________________________________________________
          Name:
          Title:


PLEASE RETURN THE COMPLETED AND EXECUTED NOTICE AND QUESTIONNAIRE FOR RECEIPT ON
OR BEFORE         ,2003 TO THE COMPANY AT:

                      ____________________________________
                      ____________________________________
                      ____________________________________
                      ____________________________________
                      ____________________________________

                                       25

<PAGE>

                                                                       Exhibit 1
                                                                   to Appendix A

              NOTICE OF TRANSFER PURSUANT TO REGISTRATION STATEMENT

Medarex, Inc,.
707 State Road, #206
Princeton, New Jersey 08540

Attention: W. Bradford Middlekauff, Senior Vice President, General Counsel &
           Secretary

Wilmington Trust Company
Rodney Square North
1100 North Market Street,
Wilmington, Delaware 19090

Attention: Corporate Trust Office

               Re:  Medarex, Inc. (the "Company")
                    4.25% Convertible Senior Notes due 2010 (the "Notes")

Dear Sirs:

          Please be advised that _____________________ has transferred
$___________ aggregate principal amount of the above-referenced Notes or shares
of the Company's common stock, issued upon conversion, repurchase or redemption
of Notes, pursuant to an effective Registration Statement on Form S-3 (File No.
333-____) filed by the Company.

          We hereby certify that the prospectus delivery requirements, if any,
of the Securities Act of 1933, as amended, have been satisfied with respect to
the transfer described above and that the above-named beneficial owner of the
Notes or common stock is named as a selling securityholder in the Prospectus
dated [date], or in amendments or supplements thereto, and that the aggregate
principal amount of the Notes or number of shares of common stock transferred
are [a portion of] the Notes or shares of common stock listed in such Prospectus
as amended or supplemented opposite such owner's name.

Dated:

                                                        Very truly yours,

                                                        ________________________
                                                        (Name)

                                              By:       ________________________
                                                        (Authorized Signature)

                                       26