EXHIBIT 10.3

                              STANDSTILL AGREEMENT

            THIS STANDSTILL AGREEMENT (the "AGREEMENT") is made as of August 24,
2001, by and among TRIANGLE PHARMACEUTICALS, INC., a Delaware corporation (the
"COMPANY"), with its principal offices at 4 University Place, 4611 University
Drive, Durham, North Carolina 27707 and WARBURG PINCUS PRIVATE EQUITY VIII,
L.P., a Delaware limited partnership (the "PURCHASER"), with its principal
offices at 466 Lexington Avenue, New York, New York 10017, and shall be
effective subject to and commencing as of the Closing Date (as such term is
defined in the Stock Purchase Agreement (as hereinafter defined)) (the
"EFFECTIVE DATE").

                                    RECITALS

            WHEREAS, the Company and Purchaser are parties to a certain Common
Stock Purchase Agreement of even date herewith (the "STOCK PURCHASE AGREEMENT")
pursuant to which the Company has agreed to issue and sell, and Purchaser has
agreed to purchase, up to 28,301,887 shares of Common Stock of the Company; and

            WHEREAS, in order to induce the Company to enter into the Stock
Purchase Agreement and to induce Purchaser to purchase shares of the Company's
Common Stock pursuant to the Stock Purchase Agreement, the Company and Purchaser
are entering into this Agreement to provide each other with certain assurances
and document certain other matters as set forth herein.

            NOW, THEREFORE, in consideration of the mutual covenants contained
in this Agreement, the Company and the Purchaser agree as follows:

                                    SECTION 1

                                   STANDSTILL

      1.1. STANDSTILL. Commencing as of the Effective Date and for so long as
the Purchaser beneficially owns (within the meaning of Rule 13d-3 under the
Securities Exchange Act of 1934, as amended (the "EXCHANGE ACT")) at least 5% of
the then outstanding Common Stock of the Company:

            (a) Purchaser (including all Affiliates) shall not acquire or agree
to acquire, publicly offer, or make any public proposal with respect to the
possible acquisition of "beneficial ownership" (within the meaning of Rule 13d-3
under the Exchange Act) of any voting securities of the Company, any securities
convertible into or exchangeable for voting securities of the Company, or any
other right to acquire voting securities of the Company, except by way of stock
dividends or other distributions or offerings made available to holders of
securities of the Company generally, from the Company or any other person or
entity, if after giving effect to such acquisition of additional shares, the
total beneficial ownership (within the meaning of Rule 13d-3 under the Exchange
Act) of Purchaser (together with all of its Affiliates) shall be greater than
the Permitted Percentage (as such term is defined in the Rights Agreement dated
as of February 1, 1999 between the Company and American Stock Transfer & Trust
Company, as Rights Agent, as amended) (the "BENEFICIAL OWNERSHIP LIMITATION")
without the prior written consent of the Company, which consent may be withheld
in its sole discretion; provided, however, that it shall not be a violation of
the prohibition contained in this Section 1.1(a) if Purchaser or any of its
Affiliates shall exceed the Beneficial Ownership Limitation solely as a

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result of an acquisition or retirement of shares of securities of the Company by
the Company which, by reducing the number of shares outstanding, increases the
proportionate number of shares of securities beneficially owned by Purchaser or
any of its Affiliates, provided that Purchaser and its Affiliates do not
thereafter acquire beneficial ownership of additional shares of securities of
the Company while still exceeding the Beneficial Ownership Limitation; and

            (b) neither Purchaser nor any Affiliate shall (i) make, or in any
way participate, directly or indirectly, in any "solicitation" of "proxies" to
vote (as such terms are used in the proxy rules of the Exchange Act) or seek to
advise, encourage or influence any person or entity with respect to the voting
of any shares of capital stock of the Company, initiate, propose or otherwise
solicit stockholders of the Company for the approval of one or more stockholder
proposals or induce or attempt to induce any other individual, firm,
corporation, partnership or other entity to initiate any stockholder proposal;
(ii) deposit any securities of the Company having the right to vote generally in
any election of directors of the Company ("VOTING STOCK") into a voting trust or
subject any shares of Voting Stock to any arrangement or agreement with respect
to the voting of such securities, where the activities of such voting trust,
arrangement or agreement would constitute a violation of the terms of this
Agreement; (iii) participate in a "13D Group" (as defined below) with respect to
any securities of the Company, where the activities of such 13D Group would
constitute a violation of the terms of this Agreement; (iv) make any public
announcement with respect to, or submit a proposal for, or offer of (with or
without conditions) any business combination, merger, acquisition,
restructuring, recapitalization, tender or exchange offer or other similar
transaction involving the Company, or its securities or a material portion of
its assets; (v) arrange, or in any way participate, directly or indirectly, in
any financing of a third party for the purchase by such party of any voting
securities or securities convertible or exchangeable into or exercisable for any
voting securities, or assets of the Company, except for such securities or
assets as are then being offered for sale by the Company or any of its
Affiliates; (vi) make any request or proposal to amend, waive or terminate any
provision of this paragraph; or (vii) initiate any discussions, negotiations,
arrangements or understandings with any third party with respect to the Company
in connection with any matters referred to in clauses (i) through (vi) above;
provided, however, that nothing in this Section 1.1(b), shall prohibit the
Purchaser from: (x) exercising its rights to designate members to the Company's
Board of Directors in accordance with Section 8.1 of the Stock Purchase
Agreement; or (y) voting its shares of Common Stock of the Company in favor of,
or seeking to advise, encourage or influence any person or entity solely with
respect to the voting of any shares of capital stock of the Company in favor of,
the election of the members designated in accordance with Section 8.1 of the
Stock Purchase Agreement or the matters recommended by the Board of Directors of
the Company in the proxy statement referenced in Section 8.3 of the Stock
Purchase Agreement. Each party agrees to promptly advise the other party of any
inquiry or proposal made by or to it with respect to any of the foregoing.

      1.2. DEFINITIONS.

            (a) "AFFILIATE" as used herein shall have the meaning ascribed to it
in Rule 12b-2 under the Exchange Act, as in effect on the date of this
Agreement.

            (b) "PERSON" as used herein shall mean any individual, corporation,
partnership, firm, association, unincorporated organization, joint venture,
trust or other entity, and shall include any successor (by merger or otherwise)
of such entity, or any of the foregoing acting together as a group, but shall
specifically exclude Purchaser (or any Affiliate of Purchaser or any 13D Group
of which Purchaser is a member).


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            (b) "13D GROUP" as used herein shall mean any group of Persons
formed for the purpose of acquiring, holding, voting or disposing of Voting
Stock, which would be required under Section 13(d) of the Exchange Act, and the
rules and regulations thereunder (as in effect, and based on legal
interpretations thereof existing, on the date hereof), to file a statement on
Schedule 13D with the Securities and Exchange Commission as a "person" within
the meaning of Section 13(d)(3) of the Exchange Act if such group beneficially
owned Voting Stock representing more than 5% of any class of Voting Stock then
outstanding.

      1.3. EQUITABLE RELIEF. Each party agrees that money damages would be both
incalculable and an insufficient remedy for any breach of this Agreement by such
party hereto or by its representatives, and that any such breach would cause the
non-breaching party irreparable harm. Each party hereto also agrees that, in
addition to all other remedies available to such party, each party shall be
entitled to specific performance and injunctive or other equitable relief as a
remedy for any breach of this Agreement. In addition, each party hereto further
agrees to waive, and to use its best efforts to cause its representatives to
waive, any requirement for the securing or posting of any bond in connection
with any breach or threatened breach of this Agreement.

      1.4. FIDUCIARY DUTY OF DIRECTORS. Notwithstanding anything to the contrary
in this Section 1, (i) the provisions of this Section 1 shall not limit or
restrict any designees of the Purchaser who are members of the Company's Board
of Directors pursuant to Section 8.1 of the Stock Purchase Agreement from taking
any actions (consistent with their fiduciary duty to the Company and its
stockholders) in their capacities as such members of the Company's Board of
Directors, and (ii) this Section 1 shall not affect the Company's obligations
under Section 8.1 of the Stock Purchase Agreement (relating to Board of Director
nominations).

                                    SECTION 2

                                  MISCELLANEOUS

      2.1. WAIVERS AND AMENDMENTS. The terms of this Agreement may be waived or
amended only with the written consent of the Company and Purchaser.

      2.2. GOVERNING LAW. This Agreement shall be governed in all respects by
and construed in accordance with the laws of the State of Delaware without any
regard to conflicts of laws principles.

      2.3. SUCCESSORS AND ASSIGNS. The provisions hereof shall inure to the
benefit of, and be binding upon, the successors and permitted assigns of the
parties to this Agreement. Notwithstanding the foregoing, neither party shall
assign this Agreement without the prior written consent of the other party,
except that this Agreement may be assigned by either party without such prior
written consent to any entity that acquires all or substantially all of its
business, whether by merger, consolidation, sale of assets or other similar
transaction.

      2.4. ENTIRE AGREEMENT. This Agreement and the Stock Purchase Agreement
constitute the full and entire understanding and agreement between the parties
with regard to the subjects hereof. The parties hereto hereby agree to maintain
as confidential the existence and terms of this Agreement unless written consent
is obtained by the other regarding the proposed disclosure. Notwithstanding the
foregoing, should disclosure be otherwise required by law or by any regulatory
agency, the parties hereby agree to cooperate in good faith to limit


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disclosure to a mutually agreeable extent and to obtain confidential treatment
or a protective order.

      2.5. NOTICES, ETC. All notices and other communications required or
permitted under this Agreement shall be in writing and may be delivered in
person, by facsimile, overnight delivery service or registered or certified
United States mail, addressed to the Company or the Purchaser, as the case may
be, at their respective addresses set forth below, or at such other address as
the Company or the Purchaser shall have furnished to the other party in writing:

      If to the Company:

            Triangle Pharmaceuticals, Inc.
            4 University Place
            4611 University Drive
            Durham, North Carolina 27707
            Telephone: 919-493-5980
            Facsimile: 919-493-5925
            Attention: Andrew Finkle, Esq.

      Copy to:

            Smith, Anderson, Blount, Dorsett, Mitchell & Jernigan, LLP
            2500 First Union Capitol Center
            Raleigh, North Carolina 27602
            Telephone: 919-821-1220
            Facsimile: 919-821-6800
            Attention: Gerald F. Roach, Esq.

      If to the Purchaser:

            Warburg Pincus Private Equity VIII, L.P.
            466 Lexington Avenue
            New York, New York 10017
            Telephone: (212) 878-0600
            Facsimile: (212) 878-9361
            Attention: Mr. Jonathan Leff

      Copy to:

            Willkie Farr & Gallagher
            787 Seventh Avenue
            New York, New York  10019
            Telephone: (212) 728-8230
            Facsimile: (212) 728-8111
            Attention: Peter H. Jakes, Esq.

            All notices and other communications shall be effective upon actual
receipt thereof by the person to whom notice is directed.


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      2.6. SEVERABILITY. If any provision of this Agreement shall be judicially
determined to be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

      2.7. COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which shall be an original, but all of which together
shall constitute one instrument.

      2.8. EXPENSES. Except as set forth in Section 2.11 hereof and in Section
17 of the Stock Purchase Agreement, the Company and Purchaser shall each bear
its own expenses incurred on its behalf with respect to this Agreement and the
transactions contemplated hereby, including fees of legal counsel.

      2.9. NO THIRD PARTY RIGHTS. Except where expressly provided to the
contrary, nothing in this Agreement shall create or be deemed to create any
rights in any person or entity not a party of this Agreement.

      2.10. FEDERAL SECURITIES LAW CHANGES. To the extent necessary to give
effect to the agreements and understandings of the parties set forth in this
Agreement, any reference in this Agreement to any forms, rules, regulations or
procedures of the Securities and Exchange Commission or any provision of the
Securities Act of 1933, as amended, or the Exchange Act existing as of the date
of this Agreement shall be deemed to refer to any modifying, supplementing or
succeeding rules, regulations, procedures or provisions as may exist from time
to time after the date of this Agreement.

      2.11. ATTORNEYS' FEES. If any action at law or in equity is necessary to
enforce or interpret the terms of this Agreement, the prevailing party shall be
entitled to reasonable attorneys' fees, costs and necessary disbursements in
addition to any other relief to which such party may be entitled.

                         (SIGNATURES ON FOLLOWING PAGE)


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                  [SIGNATURE PAGE TO THE STANDSTILL AGREEMENT]

      IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their duly authorized representatives as of the day and year first
above written.

                                        TRIANGLE PHARMACEUTICALS, INC.

                                        By:        /s/ Chris A. Rallis
                                            ------------------------------------
                                            Name:  Chris A. Rallis
                                            Title: President and Chief Operating
                                                   Officer


                                        WARBURG PINCUS PRIVATE EQUITY VIII, L.P.

                                        By: Warburg, Pincus & Co., its General
                                            Partner

                                            By:    /s/ Jonathan Leff
                                                   -----------------------------
                                                   Name: Jonathan Leff
                                                   Title: Managing Director


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