Document:

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                                                                Exhibit 10.18

                             CUSEEME NETWORKS, INC.

                          Executive Retention Agreement

      THIS EXECUTIVE RETENTION AGREEMENT by and between CUseeMe Networks, Inc.,
a Delaware corporation (the "Company"), and Christine J. Cox (the "Executive")
is made as of December 1, 2000 (the "Effective Date").

      WHEREAS, the Company recognizes that, as is the case with many
publicly-held corporations, the possibility of a change in control of the
Company exists and that such possibility, and the uncertainty and questions that
it may raise among key personnel, may result in the departure or distraction of
key personnel to the detriment of the Company and its stockholders, and

      WHEREAS, the board of directors of the Company (the "Board") has
determined that appropriate steps should be taken to reinforce and encourage the
continued employment and dedication of the Executive without distraction from
the possibility of a change in control of the Company and related events and
circumstances.

      NOW, THEREFORE, as an inducement for and in consideration of the Executive
remaining in its employ, the Company agrees that the Executive shall receive the
severance benefits set forth in this Agreement in the event the Executive's
employment with the Company is terminated under the circumstances described
below subsequent to a Change in Control (as defined in Section 1.1).

1. Key Definitions.

      As used herein, the following terms shall have the following respective
meanings:

      1.1. "Change in Control" means an event or occurrence set forth in any one
or more of subsections (a) through (d) below (including an event or occurrence
that constitutes a Change in Control under one of such subsections but is
specifically exempted from another such subsection):

            (a)   the acquisition by an individual, entity or group (within the
                  meaning of Section 13(d)(3) or 14(d)(2) of the Securities
                  Exchange Act of 1934, as amended) (a "Person") of beneficial
                  ownership of any capital stock of the Company if, after such
                  acquisition, such Person beneficially owns (within the meaning
                  of Rule 13d-3 promulgated under the Securities Exchange Act of
                  1934, as amended) 30% or more of either (i) the
                  then-outstanding shares of common stock of the Company (the
                  "Outstanding Company Common Stock") or (ii) the combined
                  voting power of the then-outstanding securities of the Company
                  entitled to vote generally in the election of directors (the
                  "Outstanding Company Voting Securities"); provided, however,
                  that the following acquisitions shall be excluded from this
                  subsection (a): (1) any acquisition directly from the Company
                  (excluding an acquisition pursuant to the exercise, conversion
                  or exchange of any security exercisable for, convertible into
                  or exchangeable for common stock or voting securities of the
                  Company, unless the Person exercising, converting or
                  exchanging such security acquired such security directly from
                  the Company or an underwriter or agent of the Company), (2)
                  any acquisition by the Company, or (3) any acquisition by any
                  employee benefit plan (or related trust) sponsored or
                  maintained by the Company or any corporation controlled by the
                  Company;

            (b)   such time as the Continuing Directors do not constitute a
                  majority of the Board (including, if applicable, the board of
                  directors of a successor corporation to the

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                  Company), where the term "Continuing Director" means at any
                  date a member of the Board (i) who was a member of the Board
                  on the date of the execution of this Agreement or (ii) who was
                  nominated or elected subsequent to such date by at least a
                  majority of the directors who were Continuing Directors at the
                  time of such nomination or election or whose election to the
                  Board was recommended or endorsed by at least a majority of
                  the directors who were Continuing Directors at the time of
                  such nomination or election, provided, however, that there
                  shall be excluded from this clause (ii) any individual whose
                  initial assumption of office occurred as a result of an actual
                  or threatened election contest with respect to the election or
                  removal of directors or other actual or threatened
                  solicitation of proxies or consents, by or on behalf of a
                  person other than the Board; or

            (c)   the consummation of a merger, consolidation, reorganization,
                  recapitalization or statutory share exchange involving the
                  Company or a sale or other disposition of all or substantially
                  all of the assets of the Company (a "Business Combination"),
                  unless, immediately following such Business Combination, each
                  of the following two conditions is satisfied: (i) all or
                  substantially all of the individuals and entities who were the
                  beneficial owners of the Outstanding Company Common Stock and
                  Outstanding Company Voting Securities immediately prior to
                  such Business Combination beneficially own, directly or
                  indirectly, more than 50% of the then-outstanding shares of
                  common stock and the combined voting power of the
                  then-outstanding securities entitled to vote generally in the
                  election of directors, respectively, of the resulting or
                  acquiring corporation in such Business Combination (which
                  shall include a corporation that as a result of such
                  transaction owns the Company or substantially all of the
                  Company's assets either directly or through one or more
                  subsidiaries) (such resulting or acquiring corporation is
                  referred to herein as the "Acquiring Corporation") in
                  substantially the same proportions as their ownership,
                  immediately prior to such Business Combination, of the
                  Outstanding Company Common Stock and Outstanding Company
                  Voting Securities, respectively; and (ii) no Person (excluding
                  the Acquiring Corporation or any employee benefit plan (or
                  related trust) maintained or sponsored by the Company or by
                  the Acquiring Corporation) beneficially owns, directly or
                  indirectly, 30% or more of the then-outstanding shares of
                  common stock of the Acquiring Corporation, or of the combined
                  voting power of the then-outstanding securities of such
                  corporation entitled to vote generally in the election of
                  directors (except to the extent that such ownership existed
                  prior to the Business Combination).

      1.2. "Change in Control Date" means the first date during the Term (as
defined in Section 2) on which a Change in Control occurs. Anything in this
Agreement to the contrary notwithstanding, if (a) a Change in Control occurs,
(b) the Executive's employment with the Company is terminated prior to the date
on which the Change in Control occurs, and (c) it is reasonably demonstrated by
the Executive that such termination of employment (i) was at the request of a
third party who has taken steps reasonably calculated to effect a Change in
Control or (ii) otherwise arose in connection with or in anticipation of a
Change in Control, then for all purposes of this Agreement the "Change in
Control Date" shall mean the date immediately prior to the date of such
termination of employment.

      1.3. "Cause" means:

            (a)   the Executive's willful and continued failure to substantially
                  perform her reasonable assigned duties as an officer of the
                  Company (other than any such failure resulting from incapacity
                  due to physical or mental illness or any failure after the
                  Executive gives notice of termination for Good Reason), which
                  failure is not cured within 30 days after a written demand for
                  substantial performance is received by the Executive from the
                  Board that

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                  specifically identifies the manner in which the Board believes
                  the Executive has not substantially performed the Executive's
                  duties; or

            (b)   the Executive's willful engagement in illegal conduct or gross
                  misconduct that is materially and demonstrably injurious to
                  the Company.

For purposes of this Section 1.3, no act or failure to act by the Executive
shall be considered "willful" unless it is done, or omitted to be done, in bad
faith and without reasonable belief that the Executive's action or omission was
in the best interests of the Company.

      1.4. "Good Reason" means the occurrence, without the Executive's written
consent, of any of the events or circumstances set forth in clauses (a) through
(d) below. Notwithstanding the occurrence of any such event or circumstance,
such occurrence shall not be deemed to constitute Good Reason if, prior to the
Date of Termination specified in the Notice of Termination (each as defined in
Section 3.2(a)) given by the Executive in respect thereof, such event or
circumstance has been fully corrected and the Executive has been reasonably
compensated for any losses or damages resulting therefrom (provided that such
right of correction by the Company shall only apply to the first Notice of
Termination for Good Reason given by the Executive):

            (a)   a reduction in the Executive's annual base salary as in effect
                  immediately prior to the earliest to occur of (i) the Change
                  in Control Date, (ii) the date of the execution by the Company
                  of the initial written agreement or instrument providing for
                  the Change in Control and (iii) the date of the adoption by
                  the Board of a resolution providing for the Change in Control
                  (with the earliest to occur of such dates referred to herein
                  as the "Measurement Date");

            (b)   the failure by the Company to (i) continue in effect any
                  material compensation or benefit plan or program (including
                  any life insurance, medical, health and accident or disability
                  plan and any vacation program or policy) (a "Benefit Plan") in
                  which the Executive participates or that is applicable to the
                  Executive immediately prior to the Measurement Date, unless an
                  equitable arrangement (embodied in an ongoing substitute or
                  alternative plan) has been made with respect to such plan or
                  program, (ii) continue the Executive's participation therein
                  (or in such substitute or alternative plan) on a basis not
                  materially less favorable, both in terms of the amount of
                  benefits provided and the level of the Executive's
                  participation relative to other participants, than the basis
                  existing immediately prior to the Measurement Date or (iii)
                  award cash bonuses to the Executive in amounts and in a manner
                  substantially consistent with past practice in light of the
                  Company's financial performance;

            (c)   the failure of the Company to obtain the agreement, in a form
                  reasonably satisfactory to the Executive, from any successor
                  to the Company to assume and agree to perform this Agreement,
                  as required by Section 6.1; or

            (d)   any failure of the Company to pay or provide to the Executive
                  any portion of the Executive's compensation or benefits due
                  under any Benefit Plan within seven days of the date such
                  compensation or benefits are due, or any material breach by
                  the Company of any employment agreement with the Executive.

The Executive's right to terminate her employment for Good Reason shall not be
affected by her incapacity due to physical or mental illness.

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2. Term of Agreement.

      This Agreement, and all rights and obligations of the parties hereunder,
shall take effect upon the Effective Date and shall expire upon (a) the
expiration of the Term (as defined below) if a Change in Control has not
occurred during the Term or (b) the date 12 months after the Change in Control
Date, if the Executive is still employed by the Company as of such date (c) the
fulfillment by the Company of all of its obligations under Sections 4 and 5.2 if
a Change in Control has occurred during the Term. "Term" shall mean the period
commencing as of the Effective Date and continuing in effect through December
31, 2003; provided, however, that commencing on January 1, 2004 and each January
1 thereafter, the Term shall be automatically extended for one additional year
unless, not later than 180 days prior to the scheduled expiration of the Term
(or any extension thereof), the Company shall have given the Executive written
notice that the Term will not be extended.

3. Employment Status; Termination Following Change in Control.

      3.1. Not an Employment Contract. The Executive acknowledges that this
Agreement does not constitute a contract of employment or impose on the Company
any obligation to retain the Executive as an employee. The Company acknowledges
that this Agreement does not prevent the Executive from terminating employment
at any time. If the Executive's employment with the Company terminates for any
reason and subsequently a Change in Control shall occur, the Executive shall not
be entitled to any benefits hereunder except as otherwise provided pursuant to
Section 1.2.

      3.2. Termination of Employment.

            (a) If the Change in Control Date occurs during the Term, any
      termination of the Executive's employment by the Company or by the
      Executive within 12 months following the Change in Control Date (other
      than due to the death of the Executive) shall be communicated by a written
      notice to the other party hereto (the "Notice of Termination"), given in
      accordance with Section 6.1. Any Notice of Termination shall: (i) indicate
      the specific termination provision (if any) of this Agreement relied upon
      by the party giving such notice; (ii) to the extent applicable, set forth
      in reasonable detail the facts and circumstances claimed to provide a
      basis for termination of the Executive's employment under the provision so
      indicated; and (iii) specify the Date of Termination (as defined below).
      The effective date of an employment termination (the "Date of
      Termination") shall be the close of business on the date specified in the
      Notice of Termination (which date may not be less than 15 days or more
      than 120 days after the date of delivery of such Notice of Termination),
      in the case of a termination other than one due to the Executive's death,
      or the date of the Executive's death, as the case may be.

            (b) The failure by the Executive or the Company to set forth in the
      Notice of Termination any fact or circumstance that contributes to a
      showing of Good Reason or Cause shall not waive any right of the Executive
      or the Company, respectively, hereunder or preclude the Executive or the
      Company, respectively, from asserting any such fact or circumstance in
      enforcing any right of the Executive or the Company, respectively,
      hereunder.

            (c) Any Notice of Termination for Cause given by the Company must be
      given within 90 days of the occurrence of the event(s) or circumstance(s)
      that constitute(s) Cause. Prior to any Notice of Termination for Cause
      being given (and prior to any termination for Cause being effective), the
      Executive shall be entitled to a hearing before the Board at which she
      may, at her election, be represented by counsel and at which she shall
      have a reasonable opportunity to be heard. Such hearing shall be held on
      not less than 15 days' prior written notice to the Executive stating the
      Board's intention to terminate the Executive for Cause and stating in
      detail the particular event(s) or circumstance(s) that the Board believes
      constitutes Cause for termination.

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            (d) Any Notice of Termination for Good Reason given by the Executive
      must be given within 90 days of the occurrence of the event(s) or
      circumstance(s) that constitute(s) Good Reason.

4. Benefits to Executive.

      4.1. Acceleration of Options. If the Change in Control Date occurs during
the Term, then, effective upon the Change in Control Date, (a) each option to
purchase shares of Common Stock of the Company held by the Executive as of the
Change in Control Date shall become immediately exercisable in full and (b)
notwithstanding any provision in any applicable option agreement to the
contrary, each such option shall continue to be exercisable by the Executive (to
the extent such option was exercisable on the Date of Termination) for a period
of six months following the Date of Termination. Notwithstanding the foregoing
provisions of this Section 4(1), if the Change in Control is intended to be
accounted for as a "pooling of interests" for financial accounting purposes, and
if any change or changes to be effected by clause (a) or (b) of the preceding
sentence would preclude accounting for the Change in Control as a "pooling of
interests" for financial accounting purposes, then such change or changes shall
not occur upon the Change in Control.

      4.2. Severance Payment. If the Change in Control Date occurs during the
Term and the Executive's employment with the Company terminates within 12 months
following the Change in Control Date, the Executive shall be entitled to the
following benefits:

            (a) If the Executive's employment with the Company is terminated by
      the Company (other than for Cause, Disability or Death) or by the
      Executive for Good Reason following the Change in Control Date, then the
      Executive shall be entitled to the following benefits:

                  (i)   the Company shall pay to the Executive in a lump sum in
                        cash within 30 days after the Date of Termination the
                        aggregate of the following amounts:

                        (A)   the sum of (1) the Executive's base salary through
                              the Date of Termination, (2) the product of (x)
                              the annual bonus paid or payable (including any
                              bonus or portion thereof which has been earned but
                              deferred) for the most recently completed fiscal
                              year and (y) a fraction, the numerator of which is
                              the number of days in the current fiscal year
                              through the Date of Termination, and the
                              denominator of which is 365, and (3) the amount of
                              any compensation previously deferred by the
                              Executive (together with any accrued interest or
                              earnings thereon) and any accrued vacation pay, in
                              each case to the extent not previously paid (the
                              sum of the amounts described in clauses (1), (2)
                              and (3) being referred to as the "Accrued
                              Obligations"); and

                        (B)   the Executive's highest annual base salary during
                              the five-year period prior to the Change in
                              Control Date;

                  (ii)  for one year after the Date of Termination, or such
                        longer period as may be provided by the terms of the
                        appropriate plan, program, practice or policy, the
                        Company shall continue to provide benefits to the
                        Executive and the Executive's family at least equal to
                        those which would have been provided to them if the
                        Executive's employment had not been terminated, in
                        accordance with the applicable Benefit Plans in effect
                        on the Measurement Date or, if more favorable to the
                        Executive and her family, in effect generally at any
                        time thereafter with respect to other peer executives of
                        the Company and its affiliated companies; provided that
                        if the Executive becomes re-employed with another
                        employer and is eligible to receive a particular type of
                        benefits (e.g., health insurance benefits) from such

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                        employer on terms at least as favorable to the Executive
                        and her family as those being provided by the Company,
                        then the Company shall no longer be required to provide
                        those particular benefits to the Executive and her
                        family;

                  (iii) to the extent not previously paid or provided, the
                        Company shall timely pay or provide to the Executive any
                        other amounts or benefits required to be paid or
                        provided or which the Executive is eligible to receive
                        following the Executive's termination of employment
                        under any plan, program, policy, practice, contract or
                        agreement of the Company and its affiliated companies
                        (such other amounts and benefits being referred to as
                        the "Other Benefits"); and

                  (iv)  for purposes of determining eligibility (but not the
                        time of commencement of benefits) of the Executive for
                        retiree benefits to which the Executive is entitled, the
                        Executive shall be considered to have remained employed
                        by the Company until one year after the Date of
                        Termination.

            (b) If the Executive voluntarily terminates her employment with the
      Company following the Change in Control Date, excluding a termination for
      Good Reason, or if the Executive's employment with the Company is
      terminated by reason of the Executive's death or Disability following the
      Change in Control Date, then the Company shall (i) pay the Executive (or
      her estate, if applicable), the Accrued Obligations in a lump sum in cash
      within 30 days after the Date of Termination and (ii) timely pay or
      provide to the Executive the Other Benefits.

            (c) If the Company terminates the Executive's employment with the
      Company for Cause following the Change in Control Date, then the Company
      shall (i) pay the Executive, in a lump sum in cash within 30 days after
      the Date of Termination, the sum of (A) the Executive's annual base salary
      through the Date of Termination and (B) the amount of any compensation
      previously deferred by the Executive, in each case to the extent not
      previously paid, and (ii) timely pay or provide to the Executive the Other
      Benefits.

      4.3.     Taxes.

            (a) Notwithstanding any other provision of this Agreement, in the
      event that the Company undergoes a Change in Ownership or Control (as
      defined below), the Company shall not be obligated to provide to the
      Executive a portion of any "Contingent Compensation Payments" (as defined
      below) that the Executive would otherwise be entitled to receive to the
      extent necessary to eliminate any "excess parachute payments" (as defined
      in Section 280G(b)(1) of the Internal Revenue Code of 1986, as amended
      (the "Code")) for the Executive. For purposes of this Section 4.3, the
      Contingent Compensation Payments so eliminated shall be referred to as the
      "Eliminated Payments" and the aggregate amount (determined in accordance
      with applicable Treasury Regulations) of the Contingent Compensation
      Payments so eliminated shall be referred to as the "Eliminated Amount."

            (b) For purposes of this Section 4.3, the following terms shall have
      the following respective meanings:

                  (i)   "Change in Ownership or Control" shall mean a change in
                        the ownership or effective control of the Company or in
                        the ownership of a substantial portion of the assets of
                        the Company determined in accordance with Section
                        280G(b)(2) of the Code; and

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                  (ii)  "Contingent Compensation Payment" shall mean any payment
                        (or benefit) in the nature of compensation that is made
                        or made available (under this Agreement or otherwise) to
                        a "disqualified individual" (as defined in Section
                        280G(c) of the Code) and that is contingent (within the
                        meaning of Section 280G(b)(2)(A)(i) of the Code) on a
                        Change in Ownership or Control of the Company.

            (c) Any payments or other benefits otherwise due to the Executive
      following a Change in Ownership or Control that could reasonably be
      characterized (as determined by the Company) as Contingent Compensation
      Payments shall not be made until the determination, pursuant to this
      Section 4.3(c), of which Contingent Compensation Payments shall be treated
      as Eliminated Payments. Within 30 days after each date on which the
      Executive first becomes entitled to receive (whether or not then due) a
      Contingent Compensation Payment relating to such Change in Ownership or
      Control, the Company shall determine and notify the Executive (with
      reasonable detail regarding the basis for its determinations) (i) which of
      such payments and benefits constitute Contingent Compensation Payments and
      (ii) the Eliminated Amount. Within 30 days after delivery of such notice
      to the Executive, the Executive shall notify the Company which Contingent
      Compensation Payments, or portions thereof (the aggregate amount of which,
      determined in accordance with applicable Treasury Regulations, shall be
      equal to the Eliminated Amount), shall be treated as Eliminated Payments.
      In the event that the Executive fails to notify the Company pursuant to
      the preceding sentence on or before the required date, the Contingent
      Compensation Payments (or portions thereof) that shall be treated as
      Eliminated Payments shall be determined by the Company in its absolute
      discretion. In no event shall the Company be liable to the Executive as a
      result of any factual or legal determination made by it pursuant to this
      subsection (c) or for any information supplied by it to the Executive or
      her advisors.

            (d) The provisions of this Section 4.3 are intended to apply to any
      and all payments or benefits available to the Executive under this
      Agreement or any other agreement or plan of the Company under which the
      Executive receives Contingent Compensation Payments.

      4.4. Mitigation. The Executive shall not be required to mitigate the
amount of any payment or benefits provided for in this Section 4 by seeking
other employment or otherwise. Further, except as provided in Section
4.2(a)(ii), the amount of any payment or benefits provided for in this Section 4
shall not be reduced by any compensation earned by the Executive as a result of
employment by another employer, by retirement benefits, by offset against any
amount claimed to be owed by the Executive to the Company or otherwise.

5. Disputes.

      All claims by the Executive for benefits under this Agreement shall be
directed to and determined by the Board and shall be in writing. Any denial by
the Board of a claim for benefits under this Agreement shall be delivered to the
Executive in writing and shall set forth the specific reasons for the denial and
the specific provisions of this Agreement relied upon. The Board shall afford a
reasonable opportunity to the Executive for a review of the decision denying a
claim.

6. Successors.

      6.1. Successor to Company. The Company shall require any successor
(whether direct or indirect, by purchase, merger, consolidation or otherwise) to
all or substantially all of the business or assets of the Company expressly to
assume and agree to perform this Agreement to the same extent that the Company
would be required to perform it if no such succession had taken place. Failure
of the Company to obtain an assumption of this Agreement at or prior to the
effectiveness of any succession shall be a breach of this Agreement and shall
constitute Good Reason if the Executive elects to terminate employment, except
that

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for purposes of implementing the foregoing, the date on which any such
succession becomes effective shall be deemed the Date of Termination. As used in
this Agreement, "Company" shall mean the Company as defined above and any
successor to its business or assets as aforesaid which assumes and agrees to
perform this Agreement, by operation of law or otherwise.

      6.2. Successor to Executive. This Agreement shall inure to the benefit of
and be enforceable by the Executive's personal or legal representatives,
executors, administrators, successors, heirs, distributees, devisees and
legatees.

7. Miscellaneous.

      7.1. Notice. All notices, instructions and other communications given
hereunder or in connection herewith shall be in writing. Any such notice,
instruction or communication shall be sent either (a) by registered or certified
mail, return receipt requested, postage prepaid, or (b) prepaid via a reputable
nationwide overnight courier service, in each case addressed to the Company at
542 Amherst Street, Nashua, New Hampshire 03063, and to the Executive at
_____________ (or to such other address as either the Company or the Executive
may have furnished to the other in writing in accordance herewith). Any such
notice, instruction or communication shall be deemed to have been delivered five
business days after it is sent by registered or certified mail, return receipt
requested, postage prepaid, or one business day after it is sent via a reputable
nationwide overnight courier service. Either party may give any notice,
instruction or other communication hereunder using any other means, but no such
notice, instruction or other communication shall be deemed to have been duly
delivered unless and until it actually is received by the party for whom it is
intended.

      7.2. Settlement of Disputes. All claims by the Executive for benefits
under this Agreement shall be directed to and determined by the Board and shall
be in writing. Any denial by the Board of a claim for benefits under this
Agreement shall be delivered to the Executive in writing and shall set forth the
specific reasons for the denial and the specific provisions of this Agreement
relied upon. The Board shall afford a reasonable opportunity to the Executive
for a review of the decision denying a claim.

      7.3. Severability. The invalidity or unenforceability of any provision of
this Agreement shall not affect the validity or enforceability of any other
provision of this Agreement, which shall remain in full force and effect.

      7.4. Governing Law. The validity, interpretation, construction and
performance of this Agreement shall be governed by the internal laws of the
State of New Hampshire, without regard to conflicts of law principles.

      7.5. Waivers. No waiver by the Executive at any time of any breach of, or
compliance with, any provision of this Agreement to be performed by the Company
shall be deemed a waiver of that or any other provision at any subsequent time.

      7.6. Counterparts. This Agreement may be executed in counterparts, each of
which shall be deemed to be an original but both of which together shall
constitute one and the same instrument.

      7.7. Amendments. This Agreement may be amended or modified only by a
written instrument executed by both the Company and the Executive.

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    IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the date first set forth above.

                                    CUSEEME NETWORKS, INC.

                                    By: /s/ Killko A. Caballero
                                       --------------------------------------
                                       President and Chief Executive Officer

                                    CHRISTINE J. COX

                                    /s/ Christine J. CoX
                                    -----------------------------------------

                                      -9-<PAGE>
                                                                  EXHIBIT 10.11

                          REGISTRATION RIGHTS AGREEMENT

         This Agreement is entered into as of July 17, 2000 by and among Art
Technology Group, Inc., a Delaware corporation (the "Buyer") and the
shareholders listed on Schedule A attached hereto (the "Shareholders").

                                    RECITALS

         WHEREAS, the Buyer, Art Technology Group Canada ULC, a Nova Scotia
unlimited liability corporation (the "Nova Scotia Subsidiary"), TTG Acquisition
Corp, a corporation incorporated under the Business Corporations Act (Ontario)
("TTG Corp."), Toronto Technology Group, Inc., a corporation incorporated under
the Business Corporations Act (Ontario) (the "Seller"), and the Shareholders,
have entered into a Share Exchange Agreement, dated as of July 11, 2000 (the
"Share Exchange Agreement").

         WHEREAS, under the Share Exchange Agreement each Shareholder will
receive exchangeable shares of TTG Corp ("Exchangeable Shares"), which are
exchangeable for shares of the Buyer's common stock, par value $.01 per share
("Buyer's Common Stock");

         WHEREAS, the Buyer and the Shareholders desire to provide for certain
arrangements with respect to the registration of the Buyer's Common Stock into
which the Exchangeable Shares can be converted (the "Registrable Shares," which
term shall also include any shares of Buyer Common Stock issued as, or issuable
upon the conversion or exercise of any warrant, right, or other security that is
issued as, a dividend or other distribution with respect to, or in exchange for
or in replacement of, the shares of Buyer Common Stock into which the
Exchangeable Shares can be converted) under the Securities Act;

         NOW, THEREFORE, in consideration of the mutual promises and covenants
contained in this Agreement, the parties hereto agree as follows:

1. CERTAIN DEFINITIONS.

     1.1 Capitalized terms used and not otherwise defined in this Agreement
shall have the meanings ascribed to such terms in the Share Exchange Agreement.

     1.2 As used in this Agreement, the following terms shall have the following
respective meanings:

     "COMMISSION" means the Securities and Exchange Commission, or any other
federal agency at the time administering the Securities Act.

     "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended, or
any successor federal statute, and the rules and regulations of the Commission
issued under such Act, as they each may, from time to time, be in effect.

<PAGE>

     "INITIATING HOLDERS" means the Shareholders initiating a request for
registration pursuant to Section 2.1(a).

     "PROSPECTUS" means the prospectus included in any Registration Statement,
as amended or supplemented by an amendment or prospectus supplement, including
post-effective amendments, and all material incorporated by reference or deemed
to be incorporated by reference in such Prospectus.

     "REGISTRATION STATEMENT" means a registration statement filed by the Buyer
with the Commission for a public offering and sale of securities of the Buyer
(other than a registration statement on Form S-8 or Form S-4, or their
successors, or any other form for a similar limited purpose, or any registration
statement covering only securities proposed to be issued in exchange for
securities or assets of another corporation).

     "SECURITIES ACT" means the Securities Act of 1933, as amended, or any
successor federal statute, and the rules and regulations of the Commission
issued under such Act, as they each may, from time to time, be in effect.

     "SELLING SHAREHOLDER" means any Shareholder owning Registrable Shares
included in a Registration Statement.

     "SHAREHOLDER" means each Shareholder and any persons or entities to whom
the rights granted under this Agreement are transferred by any Shareholder,
their successors or assigns, pursuant to Section 3 hereof.

2. REGISTRATION RIGHTS

     2.1  S-3 REGISTRATIONS

          (a) Not more than 60 days before, but no later than 90 days following,
each of the first, second and third anniversary of the Closing, one or more
Shareholders desiring to sell any Registrable Shares may request the Buyer, in
writing, to effect a registration on Form S-3 covering the resale to the public
by the Shareholders of such Registrable Shares; provided that the effective date
of such registration may be deferred until the date of such anniversary of the
Closing.

          (b) Upon receipt of any request for registration pursuant to this
Section 2.1, the Buyer shall promptly give written notice of such proposed
registration to all other Shareholders. Such Shareholders shall have the right,
by giving written notice to the Buyer within 30 days after the Buyer provides
its notice, to elect to have included in such registration such of their
Registrable Shares as such Shareholders may request in such notice of election,
subject in the case of an underwritten offering to the approval of the managing
underwriter as provided in Section 2.1(c) below. Thereupon, the Buyer shall, as
expeditiously as possible, use its best efforts to effect the registration on
Form S-3 (or any successor form); provided that, if the Buyer is not then
eligible to effect the registration on Form S-3, it shall effect the
registration using any other form that it is then eligible to use.

                                      -2-

<PAGE>

          (c) If the Initiating Holders intend to distribute the Registrable
Shares covered by their request by means of an underwriting, they shall so
advise the Buyer as a part of their request made pursuant to Section 2.1(a), and
the Buyer shall include such information in its written notice referred to in
Section 2.1(b). The right of any other Shareholder to include its Registrable
Shares in such registration pursuant to Section 2.1(b) shall be conditioned upon
such other Shareholder's participation in such underwriting on the terms set
forth herein. If the managing underwriter determines that the marketing factors
require a limitation of the number of shares to be underwritten, the number of
Registrable Shares to be included in a Registration Statement filed pursuant to
this Section 2.1, shall be reduced pro rata among the requesting Shareholders
based on the quotient of (1) the total number of Registrable Shares to be
included in the Registration Statement, divided by (2) the total number of
Registrable Shares that request registration.

          (d) The Initiating Holders shall have the right to select the managing
underwriter(s) for any underwritten offering requested pursuant to Section
2.1(a), subject to the approval of the Buyer, which approval will not be
unreasonably withheld.

          (e) If at the time of any request to register Registrable Shares by
Initiating Holders pursuant to this Section 2.1, the Buyer is engaged or has
plans to engage in a registered public offering within the next 90 days, or the
Buyer certifies in writing to the Initiating Holders that, in the good faith
determination of the Buyer's Board of Directors, the interests of the Buyer's
shareholders would be materially adversely affected by the requested
registration, then the Buyer may at its option direct that such request be
delayed for a period not in excess of 90 days from the date of such request;
provided that the Buyer shall not invoke this provision more than once in any
period of twelve (12) consecutive months.

2.2  REGISTRATION PROCEDURES.

          (a) If and whenever the Buyer is required by the provisions of this
Agreement to use its best efforts to effect the registration of any Registrable
Shares under the Securities Act, the Buyer shall:

               (i) file with the Commission a Registration Statement with
respect to such Registrable Shares and use its best efforts to cause that
Registration Statement to become effective as soon as possible;

               (ii) as expeditiously as possible prepare and file with the
Commission any amendments and supplements to the Registration Statement and the
prospectus included in the Registration Statement as may be necessary to comply
with the provisions of the Securities Act (including the anti-fraud provisions
thereof) and to keep the Registration Statement effective for a period of 10
days from the effective date or such earlier time as all Registrable Shares
covered by such Registration Statement have been sold pursuant thereto,
provided, however, that if the Buyer has exercised its right pursuant to Section
2.2(c) to suspend use of a prospectus included in a Registration Statement, then
the duration of time for which the Buyer is obligated to keep such Registration
Statement effective shall be extended by the period of such suspension;

                                      -3-

<PAGE>

               (iii) as expeditiously as possible furnish to each Selling
Shareholder such reasonable numbers of copies of the Prospectus, including any
preliminary Prospectus, in conformity with the requirements of the Securities
Act, and such other documents as such Selling Shareholder may reasonably request
in order to facilitate the public sale or other disposition of the Registrable
Shares owned by such Selling Shareholder;

               (iv) as expeditiously as possible use its best efforts to
register or qualify the Registrable Shares covered by the Registration Statement
under the securities or Blue Sky laws of such states and/or Canadian provinces
as the Selling Shareholders shall reasonably request, and do any and all other
acts and things that may be necessary or desirable to enable the Selling
Shareholders to consummate the public sale or other disposition in such states
and/or Canadian provinces of the Registrable Shares owned by the Selling
Shareholder; PROVIDED, HOWEVER, that the Buyer shall not be required in
connection with this paragraph (iv) to qualify as a foreign corporation or
execute a general consent to service of process in any jurisdiction;

               (v) as expeditiously as possible, cause all such Registrable
Shares to be listed on each securities exchange or automated quotation system on
which similar securities issued by the Buyer are then listed;

               (vi) promptly provide a transfer agent and registrar for all such
Registrable Shares not later than the effective date of such registration
statement;

               (vii) promptly make available for inspection by the Selling
Shareholders, any managing underwriter participating in any disposition pursuant
to such Registration Statement, and any attorney or accountant or other agent
retained by any such underwriter or selected by the Selling Shareholders, all
financial and other records, pertinent corporate documents and properties of the
Buyer and cause the Buyer's officers, directors, employees and independent
accountants to supply all information reasonably requested by any such seller,
underwriter, attorney, accountant or agent in connection with such Registration
Statement;

               (viii) as expeditiously as possible, notify each Selling
Shareholder, promptly after it shall receive notice thereof, of the time when
such Registration Statement has become effective or a supplement to any
Prospectus forming a part of such Registration Statement has been filed; and

               (ix) as expeditiously as possible following the effectiveness of
such Registration Statement, notify each seller of such Registrable Shares of
any request by the Commission for the amending or supplementing of such
Registration Statement or Prospectus.

          (b) If the Buyer has delivered a Prospectus to the Selling
Shareholders and after having done so the Prospectus is amended to comply with
the requirements of the Securities Act, the Buyer shall promptly notify the
Selling Shareholders and, if requested, the Selling Shareholders shall
immediately cease making offers of Registrable Shares and return all
Prospectuses to the Buyer. The Buyer shall promptly provide the Selling
Shareholders with revised Prospectuses and, following receipt of the revised
Prospectuses, the Selling Shareholders shall be free to resume making offers of
the Registrable Shares.

                                      -4-
<PAGE>

          (c) In the event that, in the judgment of the Buyer, it is advisable
to suspend use of a Prospectus included in a Registration Statement due to
pending material developments or other events that have not yet been publicly
disclosed and as to which the Buyer believes public disclosure would be
detrimental to the Buyer, the Buyer shall notify all Selling Shareholders to
such effect, and, upon receipt of such notice, each such Selling Shareholder
shall immediately discontinue any sales of Registrable Shares pursuant to such
Registration Statement until such Selling Shareholder has received copies of a
supplemented or amended Prospectus or until such Selling Shareholder is advised
in writing by the Buyer that the then current Prospectus may be used and has
received copies of any additional or supplemental filings that are incorporated
or deemed incorporated by reference in such Prospectus.

     2.3 ALLOCATION OF EXPENSES. The Buyer will pay all Registration Expenses
for all registrations under this Agreement; PROVIDED, HOWEVER, that if a
registration under Section 2.1 is withdrawn at the request of the Initiating
Holders (other than as a result of information concerning the business or
financial condition of the Buyer which is made known to the Shareholders after
the date on which such registration was requested) and if the Initiating Holders
elect not to have such registration counted as a registration requested under
Section 2.1, the requesting Shareholders shall pay the Registration Expenses of
such registration pro rata in accordance with the number of their Registrable
Shares included in such registration. For purposes of this Section, the term
"Registration Expenses" shall mean all expenses incurred by the Buyer in
complying with this Agreement, including, without limitation, all registration
and filing fees, exchange listing fees, printing expenses, fees and expenses of
counsel for the Buyer, state Blue Sky fees and expenses, and the expense of any
special audits incident to or required by any such registration, but excluding
underwriting discounts, selling commissions and the fees and expenses of Selling
Shareholders' own counsel.

     2.4  INDEMNIFICATION AND CONTRIBUTION.

          (a) In the event of any registration of any of the Registrable Shares
under the Securities Act pursuant to this Agreement, the Buyer will indemnify
and hold harmless each Selling Shareholder, each underwriter of such Registrable
Shares, and each other person, if any, who controls such Selling Shareholder or
underwriter within the meaning of the Securities Act or the Exchange Act against
any losses, claims, damages or liabilities, joint or several, to which such
Selling Shareholder, underwriter or controlling person may become subject under
the Securities Act, the Exchange Act, state securities or Blue Sky laws or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of any material fact contained in any Registration Statement
under which such Registrable Shares were registered under the Securities Act,
any preliminary prospectus or final prospectus contained in the Registration
Statement, or any amendment or supplement to such Registration Statement, or
arise out of or are based upon the omission or alleged omission to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading; and the Buyer will reimburse such Selling Shareholder,
underwriter and each such controlling person for any legal or any other expenses
reasonably incurred by such Selling Shareholder, underwriter or controlling
person in connection with investigating or defending any such loss, claim,
damage, liability or action; PROVIDED, HOWEVER, that the Buyer will not be
liable in any such case to the extent that any such loss, claim, damage or
liability arises out of or is based upon any untrue statement or omission made
in such

                                      -5-
<PAGE>

Registration Statement, preliminary prospectus or prospectus, or any
such amendment or supplement, in reliance upon and in conformity with
information furnished to the Buyer, in writing, by or on behalf of such Selling
Shareholder, underwriter or controlling person specifically for use in the
preparation thereof.

          (b) In the event of any registration of any of the Registrable Shares
under the Securities Act pursuant to this Agreement, each Selling Shareholder,
severally and not jointly, will indemnify and hold harmless the Buyer, each of
its directors and officers and each underwriter (if any) and each person, if
any, who controls the Buyer or any such underwriter within the meaning of the
Securities Act or the Exchange Act, against any losses, claims, damages or
liabilities, joint or several, to which the Buyer, such directors and officers,
underwriter or controlling person may become subject under the Securities Act,
Exchange Act, state securities or Blue Sky laws or otherwise, insofar as such
losses, claims, damages or liabilities (or actions in respect thereof) arise out
of or are based upon any untrue statement or alleged untrue statement of a
material fact contained in any Registration Statement under which such
Registrable Shares were registered under the Securities Act, any preliminary
prospectus or final prospectus contained in the Registration Statement, or any
amendment or supplement to the Registration Statement, or arise out of or are
based upon any omission or alleged omission to state a material fact required to
be stated therein or necessary to make the statements therein not misleading, if
the statement or omission was made in reliance upon and in conformity with
information relating to such Selling Shareholder furnished in writing to the
Buyer by or on behalf of such Selling Shareholder specifically for use in
connection with the preparation of such Registration Statement, prospectus,
amendment or supplement; PROVIDED, HOWEVER, that the obligations of a Selling
Shareholder hereunder shall be limited to an amount equal to the net proceeds to
such Selling Shareholder of Registrable Shares sold in connection with such
registration.

          (c) Each party entitled to indemnification under this Section (the
"Indemnified Party") shall give notice to the party required to provide
indemnification (the "Indemnifying Party") promptly after such Indemnified Party
has actual knowledge of any claim as to which indemnity may be sought, and shall
permit the Indemnifying Party to assume the defense of any such claim or any
litigation resulting therefrom; PROVIDED, that counsel for the Indemnifying
Party, who shall conduct the defense of such claim or litigation, shall be
approved by the Indemnified Party (whose approval shall not be unreasonably
withheld); and, PROVIDED, FURTHER, that the failure of any Indemnified Party to
give notice as provided herein shall not relieve the Indemnifying Party of its
obligations under this Section except to the extent that the Indemnifying Party
is adversely affected by such failure. The Indemnified Party may participate in
such defense at such party's expense; PROVIDED, HOWEVER, that the Indemnifying
Party shall pay such expense if representation of such Indemnified Party by the
counsel retained by the Indemnifying Party would be inappropriate due to actual
or potential differing interests between the Indemnified Party and any other
party represented by such counsel in such proceeding; PROVIDED FURTHER that in
no event shall the Indemnifying Party be required to pay the expenses of more
than one law firm per jurisdiction as counsel for the Indemnified Party. The
Indemnifying Party also shall be responsible for the expenses of such defense if
the Indemnifying Party does not elect to assume such defense. No Indemnifying
Party, in the defense of any such claim or litigation shall, except with the
consent of each Indemnified Party, consent to entry of any judgment or enter
into any settlement which does not include as an unconditional term thereof

                                      -6-
<PAGE>

the giving by the claimant or plaintiff to such Indemnified Party of a release
from all liability in respect of such claim or litigation, and no Indemnified
Party shall consent to entry of any judgment or settle such claim or litigation
without the prior written consent of the Indemnifying Party, which consent shall
not be unreasonably withheld.

          (d) In order to provide for just and equitable contribution in
circumstances in which the indemnification provided for in this Section 2.4 is
due in accordance with its terms but for any reason is held to be unavailable to
an Indemnified Party in respect to any losses, claims, damages and liabilities
referred to herein, then the Indemnifying Party shall, in lieu of indemnifying
such Indemnified Party, contribute to the amount paid or payable by such
Indemnified Party as a result of such losses, claims, damages or liabilities to
which such party may be subject in such proportion as is appropriate to reflect
the relative fault of the Buyer on the one hand and the Selling Shareholders on
the other in connection with the statements or omissions which resulted in such
losses, claims, damages or liabilities, as well as any other relevant equitable
considerations. The relative fault of the Buyer and the Selling Shareholders
shall be determined by reference to, among other things, whether the untrue or
alleged untrue statement of material fact related to information supplied by the
Buyer or the Selling Shareholders and the parties' relative intent, knowledge,
access to information and opportunity to correct or prevent such statement or
omission. The Buyer and the Selling Shareholders agree that it would not be just
and equitable if contribution pursuant to this Section 2.4 were determined by
pro rata allocation or by any other method of allocation which does not take
account of the equitable considerations referred to above. Notwithstanding the
provisions of this paragraph of Section 2.4, (a) in no case shall any one
Selling Shareholder be liable or responsible for any amount in excess of the net
proceeds received by such Selling Shareholder from the offering of Registrable
Shares and (b) the Buyer shall be liable and responsible for any amount in
excess of such proceeds; PROVIDED, HOWEVER, that 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. Any party entitled to contribution will, promptly
after receipt of notice of commencement of any action, suit or proceeding
against such party in respect of which a claim for contribution may be made
against another party or parties under this Section, notify such party or
parties from whom contribution may be sought, but the omission so to notify such
party or parties from whom contribution may be sought shall not relieve such
party from any other obligation it or they may have thereunder or otherwise
under this Section. No party shall be liable for contribution with respect to
any action, suit, proceeding or claim settled without its prior written consent,
which consent shall not be unreasonably withheld.

     2.5 TERMINATION. All of the Buyer's obligations to register Registrable
Shares shall terminate with respect to such Registrable Shares one year after
such Registrable Shares are issued in exchange for Exchangeable Shares.

     2.6 INFORMATION BY HOLDER. Each holder of Registrable Shares included in
any registration shall furnish to the Buyer such information regarding such
holder and the distribution proposed by such holder as the Buyer may reasonably
request in writing and as shall be required in connection with any registration,
qualification or compliance referred to in this Agreement.

                                      -7-
<PAGE>

     3. ASSIGNMENT OF RIGHTS. The Shareholder may not assign any of its rights
under this Agreement except in connection with the transfer of some or all of
his, her or its Exchangeable Shares or Registrable Shares to a child or spouse,
or trust for their benefit or, in the case of a partnership, to the partners of
such partnership pursuant to a pro rata distribution, PROVIDED each such
transferee agrees in a written instrument delivered to the Buyer to be bound by
the provisions of this Agreement.

     4. GENERAL.

          (a) SEVERABILITY. The invalidity or unenforceability of any provision
of this Agreement shall not affect the validity or enforceability of any other
provision of this Agreement.

          (b) GOVERNING LAW. This Agreement shall be governed by and construed
in accordance with the internal laws of the State of Delaware (without reference
to the conflicts of law provisions thereof).

          (c) NOTICES. All notices, requests, consents, and other communications
under this Agreement shall be in writing and shall be deemed delivered (i) two
business days after being sent by registered or certified mail, return receipt
requested, postage prepaid or (ii) one business day after being sent via a
reputable nationwide overnight courier service guaranteeing next business day
delivery, in each case to the intended recipient as set forth below:

     If to the Buyer, at Art Technology Group, Inc., 25 First Street, 2nd Floor,
Cambridge MA 02141, Attention: President, or at such other address or addresses
as may have been furnished in writing by the Buyer to the Shareholders, with a
copies to David A. Westenberg, Hale and Dorr LLP, 60 State Street, Boston, MA
02109 and Linda Handman, Art Technology Group, Inc., 25 First Street, 2nd Floor,
Cambridge MA 02141; or

     If to a Shareholder, at his or its address set forth on SCHEDULE A, or at
such other address or addresses as may have been furnished to the Buyer in
writing by such Shareholder, with a copy to____________________________________.

     Any party may give any notice, request, consent or other communication
under this Agreement using any other means (including, without limitation,
personal delivery, messenger service, telecopy, first class mail or electronic
mail), but no such notice, request, consent or other communication shall be
deemed to have been duly given unless and until it is actually received by the
party for whom it is intended. Any party may change the address to which
notices, requests, consents or other communications hereunder are to be
delivered by giving the other parties notice in the manner set forth in this
Section.

     (d) COMPLETE AGREEMENT. This Agreement constitutes the entire agreement and
understanding of the parties hereto with respect to the subject matter hereof
and supersedes all prior agreements and understandings relating to such subject
matter.

     (e) AMENDMENTS AND WAIVERS. Any term of this Agreement may be amended or
terminated and the observance of any term of this Agreement may be waived
(either generally or in a particular instance and either retroactively or
prospectively), with the written

                                      -8-
<PAGE>

consent of the Buyer and the holders of at least 66% of the Registrable Shares
held by all of the Shareholders; PROVIDED, that this Agreement may be amended
with the consent of the holders of less than all Registrable Shares only in a
manner which applies to all such holders in the same fashion. Any such
amendment, termination or waiver effected in accordance with this Section 4(e)
shall be binding on all parties hereto, even if they do not execute such
consent. No waivers of or exceptions to any term, condition or provision of this
Agreement, in any one or more instances, shall be deemed to be, or construed as,
a further or continuing waiver of any such term, condition or provision.

     (f) PRONOUNS. Whenever the context may require, any pronouns used in this
Agreement shall include the corresponding masculine, feminine or neuter forms,
and the singular form of nouns and pronouns shall include the plural, and vice
versa.

     (g) COUNTERPARTS; FACSIMILE SIGNATURES. This Agreement may be executed in
any number of counterparts, each of which shall be deemed to be an original, and
all of which together shall constitute one and the same document. This Agreement
may be executed by facsimile signatures.

     (h) SECTION HEADINGS. The section headings are for the convenience of the
parties and in no way alter, modify, amend, limit or restrict the contractual
obligations of the parties.

              [THE REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLAMK]

                                      -9-

<PAGE>

         Executed as of the date first written above.

                                     ART TECHNOLOGY GROUP, INC.

                                     By:  /s/ JOSEPH T. CHUNG
                                        -----------------------------------
                                     Title:
                                           --------------------------------

                                     SHAREHOLDERS

                                     /s/ GERARD W.H. VAN LEEUWEN
                                     -----------------------------------
                                     Gerard W.H. van Leeuwen

                                     /s/ TIMOTHY F. MOODY
                                     -----------------------------------
                                     Timothy F. Moody

                                     /s/ HENRY EDWIN VAN BEILEN
                                     -----------------------------------
                                     Henry Edwin Van Beilen

                                     /s/ GLENN JAMES
                                     -----------------------------------
                                     Glenn James

                                      -10-
<PAGE>

                                                                      EXHIBIT A

                                  SHAREHOLDERS

NAME AND ADDRESS

Gerard W.H. van Leeuwen
16954 Heart Lake Road
Caledon Village, Ontario
Canada LON 1C0

Timothy F. Moody
165 Colbeck Street
Toronto, Ontario
Canada M6S 1V8

Henry Edwin Van Beilen
613 Tomahawk Crescent
Ancaster, Ontario
Canada L9G 3T4

Glenn James
R.R. #1
Puslinch, Ontario
Canada NOB 2JO

                                      -11-

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