Exhibit 4.18

                               BUY-SELL AGREEMENT

      This Buy-Sell Agreement is made effective as of ___ day of ___________ by
and between Research Triangle Consultants, Inc., a North Carolina corporation
(the "Corporation") and __________ as the holder of the options to purchase
common stock of the Corporation (the "Optionholder").


      NOW, THEREFORE, in consideration of the grant of options to the
Optionholder and the mutual promises and covenants made herein, and for other
good and valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the parties do hereby agree as follows:

                              I. SCOPE OF AGREEMENT

      This Agreement shall apply to any and all shares of capital stock or
rights to acquire shares of capital stock of the Corporation now or in the
future owned by the Optionholder however and whenever acquired by the
Optionholder, which capital stock and rights to acquire shares of capital stock
are hereinafter referred to as the "Shares."

                        II.  RESTRICTIONS ON TRANSFER.

2.1   Restrictions on Transfer. The Optionholder will not sell, transfer,
      donate, exchange or assign or in any way dispose of his or her ownership
      of any of his or her Shares of capital stock of the Corporation, either
      voluntarily or involuntarily, including, without limitation, any purported
      transfer by or pursuant to bankruptcy, attachment, divorce, equitable
      distribution, or operation of law, without the prior written consent of
      the Corporation, unless such transfer is in accordance with the terms and
      conditions of this Agreement. The Corporation agrees not to unreasonably
      withhold approval for transfers made by the Optionholder for estate
      planing purposes during his or her lifetime or by testamentary transfer,
      any or all of his or her shares of the Corporation to his or her spouse,
      any of his or her children, grandchildren or direct lineal descendants,
      whether by blood or by adoption, spouses of such issue or a trust for the
      sole benefit of those persons or any of them. In case of any such
      transfer, the transferee shall as a consideration to transfer execute and
      deliver, and be bound by, all the provisions of this Agreement and no
      further transfer of such shares shall be made by such transferee except
      back to the Optionholder who originally owned them or except in accordance
      with the provisions of this Agreement.

2.2   Void Transfers. The Corporation will not transfer on its books any Shares
      sold or transferred other than pursuant to the terms and conditions of
      this Agreement. No transferee of Shares in violation of the terms and
      conditions of this Agreement will be a record owner of such Shares nor
      will such transferee have the right to receive dividends or other
      distributions payable to the record owner of such Shares. In the event
      proper consent is obtained, such transfers shall not be effective unless
      and until the transferee executes and



      becomes a party to this Agreement and is legally bound by the terms and
      conditions herein. Any transfer of Shares in violation of the terms and
      conditions of this Agreement will be void and without effect in
      transferring any interest in such Shares to the transferee.

2.3   Lifetime Transfers.

      (i)   Offer to Corporation. The Optionholder, or transferee of the
            Optionholder, who wishes to transfer all or any part of his or her
            Shares of the Corporation (hereinafter "offeror"), other than an
            estate planning transfer approved by the Corporation as provided
            above, shall first shall submit a written offer to sell such shares
            to the Corporation at the lesser of: (A) the same price per share
            and upon the same terms and conditions offered by a bona fide
            prospective purchaser of such shares; or (B) the Fair Market Value
            determined as provided in Section 3.4 of this Agreement. Such
            written offer to the Corporation shall continue to be a binding
            offer to sell until: (1) expressly rejected by the Chief Executive
            Officer or Chief Financial Officer of the Corporation; or (2) the
            expiration of a period of thirty (30) days after delivery of such
            written offer to the Corporation, whichever shall first occur.

      (ii)  Contents of Offer. Every written offer submitted in accordance with
            the provisions of this Section 2.3 shall specifically name the
            person to whom the offeror intends to transfer the Shares, the
            number and class of the Shares which he or she intends so to
            transfer to each person and the price per share and other terms upon
            which each intended transfer is to be made. If requested by the
            Corporation, the Optionholder shall provide such other information
            as the Corporation requests. Upon the termination of all such
            written offers and the thirty (30) day period provided for in
            Section 2.3(i) above, the offeror shall be free to transfer, for a
            period of thirty (30) days thereafter, any unpurchased shares to the
            persons so named at the price per share and upon the other terms and
            conditions so named, provided that any such transferee of the Shares
            as a condition to transfer executes and deliver to the Corporation a
            counterpart of this Agreement agreeing to be bound by the right of
            first refusal in any subsequent transfer provisions of this
            Agreement.

      (iii) Delivery of Offer. Every written offer submitted to the Corporation
            shall be deemed to have been delivered when delivered in person to
            the Chief Financial Officer of the Corporation or if and when sent
            by prepaid registered or certified mail, to the Chief Financial
            Officer of the Corporation at 1135 Kildaire Farm Road, Cary, N.C.
            27511, Attention: Chief Financial Officer, or at such other address
            as the Corporation may hereafter deliver to the Optionholder at the
            address specified below.

      (iv)  Consideration Other than Cash. If any consideration to be received
            by the offeror for the shares offered is property other than cash,
            then the price per share shall be measured to the extent of the fair
            market value of such noncash consideration, which determination
            shall be made in good faith by the Board of Directors of the


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            Corporation, or a committee of the Board of Directors. Such
            determination shall be final and binding.

2.4   Closing. The closing (the "Closing") will take place at the principal
      office of the Corporation on a date specified by the Corporation, which
      shall not exceed a reasonable time after determination of the purchase
      price or at such time and place as may be mutually agreed upon by the
      parties. The selling Optionholder or his or her personal representative
      will deliver to the purchaser at Closing the certificates representing the
      Shares being purchased along with such additional documentation and
      endorsements as the purchasers may reasonably request.

2.5   Payment of Purchase Price. The purchase price of the Shares will be
      payable at Closing in cash or by certified check.

                 III. OPTION TO PURCHASE OR SELL SHARES

3.1   Option of the Corporation. The Corporation shall have the option to
      purchase all or some of the Shares at any time and from time from the
      Optionholder as the Corporation shall determine in its sole discretion for
      the Fair Market Value determined as provided in Section 3.4 of this
      Agreement.

3.2   Option of the Optionholders.

      (a)   Except if the employment of the Optionholder by the Corporation is
            terminated for Cause (as defined below), the Optionholder shall have
            the right to require the Corporation from time to time and at any
            time to purchase some or all of the Shares held by the Optionholder
            (the "Put") for a purchase price equal to the lesser of (i) the Fair
            Market Value determined as provided in Section 3.4 of this Agreement
            or (ii) the price which the Optionholder paid the Corporation to
            acquire the Share(s) the Optionholder is requiring the Corporation
            to purchase upon exercise of the Put.

      (b)   Notwithstanding subsection (a) above, the Board of Directors or a
            committee thereof, may, from time to time in its sole discretion,
            limit the aggregate amount that the Corporation may use to purchase
            Shares from Optionholders pursuant to subsection (a) above during
            any one (1) year or other period (the "Put Amount"). If an
            Optionholder exercises his Put and the Put Amount would be exceeded
            if the Corporation paid the purchase price for the Put, the
            Corporation shall so notify the Optionholder and shall purchase only
            that portion of the Shares held by the Optionholder exercising his
            Put that would not result in the Corporation exceeding the Put
            Amount. The Board of Directors or a committee thereof may adopt any
            rules it deems appropriate for allocating dollars available among
            all persons eligible to sell Shares to the Corporation.

      (c)   If the Corporation is unable to purchase some or all of the Shares
            the exercising Optionholder has requested the Corporation to
            purchase as a result of the limitation


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            in subsection (b) above, immediately after the applicable twelve
            (12) month period has ended, the Corporation shall purchase the
            Shares not previously purchased from the exercising Optionholder
            prior to purchasing any other Shares held by other Optionholders
            exercising their Put, in the manner and subject to the limitation
            set forth in this Section 3.2.

      (d)   "Cause" shall be limited to the following events: (i) drug abuse by
            Optionholder; (ii) alcohol abuse by Optionholder if it interferes
            with the efficient conduct of business by Optionholder; (iii) theft,
            embezzlement or other similar act by Optionholder of any tangible or
            intangible asset of the Corporation or any customer, supplier or
            investor of the Corporation; (iv) commission of any other criminal
            act by Optionholder (whether or not Optionholder is prosecuted and
            convicted) if such act causes or is likely to cause damage to the
            business of the Corporation; (v) a material breach by Optionholder
            of any written agreement between the Corporation and Optionholder,
            or any written policy of the Corporation known by and applicable to
            all its employees, but a mere mistake in business judgment shall not
            constitute "Cause" unless it is a part of a continuing pattern of
            bad judgment that has caused actual damage to the Corporation or its
            business, and (vi) willful failure by Optionholder to follow the
            instructions of the Board of Directors of the Corporation or an
            officer or other supervisory employee of the Corporation duly
            authorized by the Board, the Bylaws of the Corporation or an officer
            of the Corporation to give instructions to Optionholder, to the
            extent such instructions are reasonably related to the business of
            the Corporation, are given in good faith to promote the interest of
            the Corporation, would not require Optionholder to commit any
            illegal act and are not given to provide the Corporation with cause
            for terminating Optionholder.

3.3   Manner of Exercise; Closing. The Corporation or the Optionholders shall
      exercise their respective options by notice in writing given by the
      Corporation or the Optionholder to the other party, in the case of the
      Corporation, in the manner provided in Section 2.3(iii) of this Agreement,
      or, in the case of the Optionholder, at the address set forth in Schedule
      1 hereto. Closing shall take place at the time specified in the notice,
      which shall be not less than thirty (30) days following the date of
      notice. The Closing will take place as provided in Section 2.4 above and
      payment shall be made in the manner provided in Section 2.5.

3.4   Fair Market Value. The Fair Market Value of any Shares shall be the value
      determined in good faith from time to time by the Board of Directors of
      the Corporation or a committee thereof. Such determination shall be final
      and binding. If the Optionholder's employment or service is terminated by
      reason of his death or disability, all insurance proceeds payable to the
      Corporation on account of such Optionholder's death or disability shall be
      excluded in making such determination of Fair Market Value, whether or not
      such proceeds have been paid to the Corporation as of the valuation date.


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                          IV. ADMINISTRATION.

4.1   Legend on Certificates. The Corporation will take such action as is
      necessary to inscribe on each Share certificate the following legend:

            "The shares represented by this certificate, and the transfer
            thereof are subject to the provisions of a Buy-Sell Agreement dated
            as of the 1st day of July, 1998, a copy of which may be inspected at
            the principal office of the corporation. The agreement, among other
            things, restricts sale, transfer or hypothecation of the shares. No
            transfer of ownership of the shares represented by this certificate
            is valid unless transferor and transferee have complied with the
            terms and conditions of the Buy-Sell Agreement prior to such
            transfer."

4.2   Employment. Employment of the Optionholder by the Corporation, if any, is
      subject to the continued approval of the management and/or the Board of
      Directors of the Corporation. Neither the ownership of Shares nor this
      Agreement confers on any Optionholder any expectation of or right to
      employment. The remedies provided in a written employment agreement will
      constitute the Optionholder's sole remedy for termination of employment.

4.3   Term. The term of this Agreement will commence upon its execution and
      terminate on the earlier to occur of the following:

      (i)   dissolution and completion of the liquidation of the Corporation;

      (ii)  the bankruptcy, receivership or dissolution of the Corporation;

      (iii) the effectiveness of a registration statement under the Securities
            Act of 1933, as amended, relating to a bona fide, firm commitment
            underwriting of the Corporation's common stock; provided, however,
            that as a condition to termination of the Corporation may in its
            sole discretion require the Optionholder to execute and deliver to
            the underwriters in the offering such form of lock-up agreement as
            the underwriters request any shareholder of the Corporation to sign;
            or

      (iv)  the mutual agreement of the parties hereto.

                              V.  MISCELLANEOUS.

5.1   Performance. Each Optionholder and the Corporation agrees to perform such
      acts as may be reasonably necessary to carry out the provisions of this
      Agreement.

5.2   Modification. This Agreement supersedes all prior agreements between the
      parties and constitutes the entire agreement between the parties on the
      subjects herein. The provisions of this Agreement may not be amended,
      deleted or modified in whole or in part without the


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express written consent of all parties to this Agreement which will be executed
with the same formality as this Agreement.

5.3   Governing  Law. This  Agreement will be subject to and governed by
      the laws of the State of North  Carolina,  without  respect to the
      principles of the choice of law or the conflicts of law.

5.4   Binding  Effect.  This Agreement will be binding upon and inure to
      the benefit of the parties  hereto,  their heirs,  successors  and
      assigns.

5.5   Severability. Each portion of this Agreement will be interpreted as
      separate and divisible, and in the event that any provision will be held
      to be void, invalid, or unenforceable, the remaining provisions of this
      Agreement will continue to be in full force and effect.

5.6   Headings. The headings used in this Agreement are included only for
      convenience of reference, and in the event of any conflict between such
      headings and the text of this Agreement, the text will control.

5.7   Notices. All notices required or referenced under this Agreement will be
      in writing, and will be deemed to have been duly given on (i) the date of
      service if served personally on the party to whom the notice is to be
      given, or (ii) if mailed on the date three (3) days after having been
      mailed to the party to whom notice is to be given by first class mail,
      postage pre-paid, registered or certified, if properly addressed to the
      party at his or her address as set forth below (or, in the case of the
      Corporation, the address set forth above), or at such other address as the
      party may hereafter designate by written notice to the remaining parties.

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

5.9   Gender.  All  references  to gender will be  interchangeable  with
      the masculine, feminine, and neuter, as applicable.

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

                              RESEARCH TRIANGLE CONSULTANTS, INC.


                              By:
                                  --------------------------------------------
                              Name:  Jeffrey LeRose
                                  --------------------------------------------
                              Title:  President  and  Chief  Executive Officer
                                  --------------------------------------------

                                  OPTIONHOLDER:


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                              Name:
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                              Address:
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