<PAGE>

                                                                   EXHIBIT 10.11

                             INVESTMENT AGREEMENT
                             --------------------
                          (Series E Preferred Stock)

     THIS IS AN INVESTMENT AGREEMENT (this "Agreement") made and dated as of
September 10, 1999 by and:

among:    GREENWICH TECHNOLOGY PARTNERS, INC., a Delaware corporation (the
-----
          "Corporation");

and:      those parties identified on the "Schedule of Investors" attached to
---
          this Agreement as Exhibit A under the heading "Investor" (each an
                            ---------
          "Initial Investor"), and the parties executing a counterpart signature
          page hereto as an additional investor (each an "Additional Investor"
          and collectively, the "Series E Investors").

     The Corporation and the Series E Investors agree as follows:

     1.   DEFINITIONS. As used in this Agreement, each of the following terms is
          -----------
used as follows:

          "Affiliate":  With respect to any particular Person, any other Person
directly or indirectly, controlling, controlled by or under common control with
such Person.

          "Books and Records":  The books and records of the Corporation.

          "Business":  The computer networking and related consulting business
conducted by the Corporation.

          "Common Stock":  As defined in Section 4.2.

          "Environmental Laws":  All Laws governing the use, storage, shipment,
handling, disposal, discharge, release, cleanup, reporting, labeling, warning,
workplace disclosure or monitoring of Hazardous Materials, or otherwise relating
to environmental pollution or environmental protection, including, as may be
applicable to environmental matters, the common law respecting nuisance,
trespass, tortious liability and strict liability.

          "Financial Statements":  The Corporation's (i) audited balance sheet
for the period ending December 31, 1998 and the related statements of income,
retained earnings and changes in financial position for such fiscal period and
(ii) unaudited balance sheet for the period ending June 30, 1999 and the related
statements of income, retained earnings and changes in financial position for
such fiscal period.

          "Hazardous Materials":  All substances, in whatever form or
concentration, which are classified as hazardous, toxic or dangerous or as
pollutants or
<PAGE>

                                      -2-

contaminants under any Environmental Laws. "Hazardous Materials" specifically
include gasoline, oil and other petroleum products, their fractions and their
constituent and residual compounds and by-products, and radon, asbestos, lead-
based paint, ureaformaldehyde and PCB's. Where under applicable Environmental
Laws a jurisdiction exercises the authority to establish stricter requirements
regarding Hazardous Materials or to define Hazardous Materials more inclusively,
the stricter requirements and more inclusive definitions shall apply with
respect to the operations of the Business which are located or conducted within
such jurisdictions or which are otherwise subject to its authority.

          "Laws":  All material laws, statutes, ordinances, rules, regulations
and other requirements having the force of law promulgated by any governmental
authority, commission, agency or body which are applicable to the Corporation or
the Business, in each case whether local, state, or federal.

          "Liabilities":  All liabilities or obligations of the Corporation of
any kind or description, whether accrued, absolute, contingent or otherwise.

          "Liens":  All liens, security interests, pledges, mortgages,
encumbrances, claims, charges, agreements and rights of others of any nature
whatsoever.

          "Losses":  Any loss, claim, liability, penalty, damage, cost or
expense, whether direct or indirect, special or consequential, including
reasonable attorney's fees.

          "Order":  Any order, writ, decree, ruling, award, injunction or other
directive or requirement having the force of law issued by any court, tribunal,
administrative agency, other governmental authority, or arbitrator, in each case
whether local, state or federal which is applicable to the Corporation.

          "Person":  Any natural person, corporation, partnership (general,
limited or otherwise), limited liability company, trust, association, joint
venture, governmental body or agency or other entity having legal status of any
kind.

          "Preferred Shareholders":  As defined in Section 2.2.

          "Preferred Shares":  All outstanding Series A Shares, Series B Shares,
Series C Shares, Series D Shares and Series E Shares.

          "Proceeding":  Any litigation, lawsuit, arbitration, mediation,
grievance, hearing, investigation or other legal, administrative, governmental
or private party proceeding or enforcement action.

          "Registration Rights Agreement":  As defined in Section 2.3.

          "Series A Shares":  Shares of Series A Preferred Stock, $.01 par value
per share, having the rights, preferences, privileges, restrictions and other
matters set forth in the Third Amended and Restated Certificate of Incorporation
of the Corporation.
<PAGE>

                                      -3-

          "Series B Shares":  Shares of Series B Preferred Stock, $.01 par value
per share, having the rights, preferences, privileges, restrictions and other
matters set forth in the Third Amended and Restated Certificate of Incorporation
of the Corporation.

          "Series C Shares":  Shares of Series C Preferred Stock, $.01 par value
per share, having the rights, preferences, privileges, restrictions and other
matters set forth in the Third Amended and Restated Certificate of Incorporation
of the Corporation.

          "Series D Shares":  Shares of Series D Preferred Stock, $.01 par value
per share, having the rights, preferences, privileges, restrictions and other
matters set forth in the Third Amended and Restated Certificate of Incorporation
of the Corporation.

          "Series D Warrants": Warrants to purchase Series D Shares.

          "Series E Shares": Shares of Series E Preferred Stock, $.01 par value
per share,  having the rights, preferences, privileges, restrictions and other
matters set forth in the Third Amended and Restated Certificate of Incorporation
of the Corporation.

          "Shareholders' Agreement":  As defined in Section 2.2.

     2.   PURPOSE AND BACKGROUND.
          ----------------------

          2.1. Sale of Series E Shares.  The Corporation desires to sell to the
               -----------------------
Series E Investors an aggregate of not more than 11,848,342 Series E Shares, and
the Series E Investors desire to purchase such Series E Shares from the
Corporation in the amounts and for the aggregate purchase prices as set forth on
the Schedule of Investors attached hereto as Exhibit A, all on the terms and
                                             ---------
conditions set forth in this Agreement.

          2.2  The Closing.
               -----------

          (a)  The initial closing ("Initial Closing") of the sale and purchase
of up to 7,582,940 of the Series E Shares under this Agreement shall take place
at the offices of Testa, Hurwitz & Thibeault, LLP, 125 High Street, Boston,
Massachusetts, at 1:00 p.m. on the date as is mutually agreeable to the Initial
Investors and the Corporation.

          (b)  An additional closing (the "Additional Closing") of the sale and
purchase of up to an additional 4,265,402 of the Series E Shares under this
Agreement shall take place at the offices of Testa, Hurwitz & Thibeault, LLP,
125 High Street, Boston, Massachusetts, at 1:00 p.m. on the date as is mutually
agreeable to the Additional Investors and the Corporation.

          (c)  The Initial Closing and the Additional Closing are each referred
to herein as a "Closing."
<PAGE>

                                      -4-

          (d)   The representations of the Corporation in Section 4 hereof and
the representations of the Series E Investors in Section 5 hereof shall speak as
of the date of the Closing in which such Series E Investor is purchasing Series
E Shares.

          2.3.  Shareholders' Agreement. At the Initial Closing, the Corporation
                -----------------------
the participating Series E Investors and the holders of the Corporation's Series
A Shares, Series B Shares, Series C Shares and Series D Shares (such holders of
Series A Shares, Series B Shares, Series C Shares, Series D Shares and Series E
Shares, collectively, after giving effect to the transactions contemplated by
this Agreement, the "Preferred Shareholders") shall enter into an Amended and
Restated Shareholders' Agreement (the "Shareholders' Agreement") setting forth,
among other matters, certain restrictions on disposition of, and options to
purchase or sell, the Preferred Shareholders' respective shares of the
Corporation's Preferred Stock.

          2.4.  Registration Rights Agreement.  At the Initial Closing, the
                -----------------------------
Corporation, the holders of Series D Shares and the participating Series E
Investors shall enter into an Amended and Restated Registration Rights Agreement
(the "Registration Rights Agreement") setting forth, among other matters,
certain obligations of the Corporation to register the Series D Shares and
Series E Shares pursuant to the Securities Act of 1933, as amended (the
"Securities Act").

          2.5   Counterpart Signature Pages.  At the Additional Closing, the
                ---------------------------
Additional Investors shall execute a counterpart signature page to this
Agreement, the Shareholders' Agreement and the Registration Rights Agreement.

     3.   PURCHASE AND SALE; USE OF PROCEEDS. Subject to the terms and
          ----------------------------------
conditions contained in this Agreement:

          3.1.  Purchase of Series E Shares.  At each Closing the Corporation
                ---------------------------
shall sell and issue to the Series E Investors participating in such Closing,
and each of the Series E Investors participating in such Closing shall purchase
from the Corporation, the number of Series E Shares set forth opposite his, her
or its name on Schedule of Investors attached hereto as Exhibit A, free and
                                                        ---------
clear of all Liens, for the respective purchase prices set forth opposite such
name on such Schedule of Investors, and which applicable purchase prices will be
paid by each Series E Investor on the date of the applicable Closing.

          3.2.  Use of Proceeds.  The Corporation shall use the proceeds from
                ---------------
the sale of the Series E Shares for working capital and general corporate
purposes, including the payment of placement agent fees and the payment of legal
fees and expenses of the Series E Investors as provided in section 10.6, for the
expansion of the Corporation's business, for capital expenditures, for potential
acquisitions and for the repayment of debt.

     4.   THE CORPORATION'S REPRESENTATIONS AND WARRANTIES. Except as set forth
          ------------------------------------------------
in the Schedule of Exceptions attached hereto as
<PAGE>

                                      -5-

Exhibit B, the Corporation makes the following representations and warranties to
---------
the Series E Investors:

          4.1.  Organization and Authority.  The Corporation is a corporation
                --------------------------
duly organized, validly existing and in good standing under the Laws of the
State of Delaware.  The Corporation has full corporate power and authority to
own its assets and to carry on the Business as presently conducted.  The
Corporation is duly qualified to do business as a foreign corporation and is in
good standing in each jurisdiction where the failure to so qualify would have a
material adverse effect on the Corporation's business, properties or financial
condition.  The Corporation has no subsidiaries and owns no capital stock or
other equity interests in any Person.  The execution, delivery and performance
of this Agreement, the Shareholders' Agreement and the Registration Rights
Agreement have been duly authorized by the Corporation's Board of Directors and
shareholders, and no further corporate or other action is required on the part
of the Corporation in order to authorize this Agreement, the Shareholders'
Agreement or the Registration Rights Agreement or the transactions contemplated
hereby or thereby, including, without limitation, the issuance of the Series E
Shares to the Series E Investors, as set forth on the Schedule of Investors and
the issuance of the shares of Common Stock upon conversion of the Series E
Shares.  Each of this Agreement, the Shareholders' Agreement and the
Registration Rights Agreement is the legal, valid and binding obligation of the
Corporation, duly enforceable against the Corporation in accordance with its
terms.

          4.2.  Capitalization.  The Corporation's authorized capital stock
                --------------
consists solely of 90,000,000 shares, 54,824,782 of which have been designated
common stock, par value $.01 per share (the "Common Stock"), of which 200,550
shares are issued and outstanding, and 35,175,218 of which have been designated
preferred stock, par value $.01 per share (the "Preferred Stock").  4,100,000 of
the authorized shares of Preferred Stock are designated as "Series A Preferred
Stock", all of which are issued and outstanding, 5,533,031 of the authorized
shares of Preferred Stock are designated as "Series B Preferred Stock", all of
which are issued and outstanding, 4,206,666 of the authorized shares of
Preferred Stock are designated as "Series C Preferred Stock", all of which are
issued and outstanding, 9,487,179 of the authorized shares of Preferred Stock
are designated as "Series D Preferred Stock", 5,213,675 of which are issued and
outstanding, and 11,848,342 of the authorized shares of Preferred Stock are
designated as "Series E Preferred Stock", none of which are issued and
outstanding prior to the date of the initial Closing.  As of the date hereof,
4,500,000 of the Corporation's authorized but unissued shares of Common Stock
have been reserved for issuance under the Corporation's 1997 Option Plan (the
"1997 Plan"), of which options to purchase 3,771,405  shares of Common Stock are
currently outstanding.  A total of 35,175,218 of the Corporation's authorized
but unissued shares of Common Stock have been reserved for issuance upon
conversion of the authorized Series A Shares, Series B Shares, Series C Shares,
Series D Shares, and Series E Shares whether or not currently issued and
outstanding.  A total of 4,273,504 of the Corporation's authorized but unissued
Series D Shares have been reserved for issuance upon exercise of the Series D
Warrants.  Except
<PAGE>

                                      -6-

as provided above, the Corporation has no other shares of capital stock reserved
for issuance, and no outstanding options or warrants related to its shares of
capital stock or any outstanding securities or obligations convertible into or
exchangeable for, or giving any Person any right to subscribe for or acquire
from the Corporation, any shares of capital stock. There are no preemptive or
other subscription rights with respect to any shares of capital stock. All of
the shares of capital stock which are issued and outstanding have been duly
authorized and validly issued and are fully paid and are nonassessable. The
Series E Shares to be issued to the Series E Investors pursuant to this
Agreement have been duly authorized and when issued in accordance with this
Agreement will be validly issued, fully paid and nonassessable. All securities
issued by the Corporation prior to the date of this Agreement have been issued
in compliance with all applicable securities laws or pursuant to a valid
exemption therefrom.

          4.3.  No Conflict or Violation.  Neither the execution of this
                ------------------------
Agreement, the Shareholders' Agreement or the Registration Rights Agreement by
the Corporation nor the performance by the Corporation of the transactions
contemplated by this Agreement, the Shareholders' Agreement or the Registration
Rights Agreement, will result in: (i) a violation of or conflict with the
Corporation's Third Amended and Restated Certificate of Incorporation or bylaws;
(ii) a violation of any Laws or any Order to which the Corporation is subject;
(iii) the imposition of any material Lien against the Corporation's assets; or
(iv) a material breach or default under any mortgage, indenture, deed of trust,
real property or personal property lease, license, material contract, or other
agreement.

          4.4.  Financial Statements.  The Financial Statements were prepared in
                --------------------
accordance with United States generally accepted accounting principles ("GAAP"),
applied on a consistent basis throughout the periods involved (except as may be
indicated in the notes thereto).  The Financial Statements present fairly in all
material respects the financial condition and results of operations of the
Corporation of and for the periods covered by the Financial Statements, subject
only to ordinary course adjustments for normal, recurring accruals resulting
from the year-end audit in the case of the June 30, 1999 financial statements.

          4.5.  Absence of Certain Changes or Events.  Since June 30, 1999, the
                ------------------------------------
Corporation has operated only in the ordinary course and there has been no:  (i)
material adverse change in the business, financial condition or results of
operations of the Corporation, (ii) damage, destruction or loss (whether or not
covered by insurance) involving any of the Corporation's assets; (iii) sale or
lease or other disposition of any of the Corporation's assets, except for
dispositions in the ordinary course; (iv) declaration or payment of any dividend
or distribution on any shares of its capital stock or other equity interests;
(v) repurchase or other acquisition of any shares of its capital stock or other
equity interests or any outstanding securities convertible into shares of
capital stock or of any option, warrant, right, call or commitment relating to
shares of capital stock or other equity interests or any outstanding securities
convertible into shares of capital stock, or, any grant to any Person of any
right to subscribe for or acquire from it, any shares of capital stock or other
equity interests; (vi) the granting or creation by the Corporation of
<PAGE>

                                      -7-

any material Lien affecting any of the Corporation's assets; or (vii) to the
Corporation's best knowledge, any transaction by the Corporation outside the
ordinary course of business.

          4.6.  Consents and Approvals.  Other than consents obtained prior to
                ----------------------
the Closing and except for the applicable requirements of the Securities Act and
state securities laws, the execution, delivery and performance by the
Corporation of this Agreement, the Shareholders' Agreement or the Registration
Rights Agreement and the transactions contemplated hereby or thereby, do not
require the consent, approval or authorization of, or any declaration, filing,
registration or notice with or to any governmental or regulatory authority, or
any other Person, except where the failure to obtain such consent would not have
a material adverse effect on the Corporation.

          4.7.  Material Agreements.  Schedule 4.7 of the Schedule of Exceptions
                -------------------
contains a complete and correct list, as of the date of this Agreement, of all
material agreements, contracts, commitments, undertakings and other obligations,
whether written or oral, involving the Corporation or otherwise relating to the
Business, which shall include but are not limited to agreements which entail a
commitment of $50,000 or more.  True and complete copies of all written
agreements, contracts and commitments listed in Schedule 4.7 of the Schedule of
Exceptions, including all amendments, have been made available to the Series E
Investors.  Each such agreement, contract or commitment is a valid and binding
agreement of the Corporation and is in full force and effect, and neither the
Corporation, nor, to the knowledge of the Corporation, any other party thereto
is in default under the terms of any such agreement, contract or commitment.

          4.8.  Absence of Litigation.  There is no material Proceeding which is
                ---------------------
either pending or, to the Corporation's best knowledge, threatened against the
Corporation or otherwise involving its assets or the Business, and there are no
outstanding Orders against the Corporation or with respect to the Business or
the Corporation's assets.

          4.9.  Compliance with Laws.  The Corporation is in compliance in all
                --------------------
material respects, with the Laws applicable to the Corporation, except where the
failure to do so would not have a material adverse effect on the Corporation.
The Corporation has complied in all material respects with the Laws applicable
to the Corporation, except where the failure to do so did not have a material
adverse effect on the Corporation.  The Corporation has not received notice of
violation or alleged violation of any Laws relating to the conduct of the
Business which has not been rectified or which remains outstanding.

          4.10. Accounts Receivable.  All accounts receivable reflected on the
                -------------------
Financial Statements and all accounts receivable of the Business that have
arisen since the date of the Financial Statements derive from bona fide
                                                              ---- ----
transactions in the ordinary course of the Business and are payable on ordinary
terms, less adequate reserves for doubtful accounts as reflected in the Books
and Records.  No person has asserted or threatened to assert any counterclaims
or offsetting claims or defenses to collection of the
<PAGE>

                                      -8-

Corporation's accounts receivable. The Books and Records as of the date of this
Agreement reflect an accurate aging of all accounts receivable. The Corporation
is not aware that any of the accounts receivables as of the date of this
Agreement are uncollectible or are likely to be uncollectible in the ordinary
course within 90 days after origination.

          4.11.  Intellectual Property.  Schedule 4.11 of the Schedule of
                 ---------------------
Exceptions contains  a true and complete listing, as they relate to or are used
in the Business, of all:  (i) trademark registrations and applications in the
United States, any state or any other jurisdiction; (ii) common law or
unregistered trademarks; (iii) tradenames, (iv) patents and patent applications;
and (v) registered copyrights (collectively, the "Intellectual Property").  No
proceedings are pending or, to the Corporation's best knowledge, threatened,
which challenge the validity of the Corporation's ownership or use of the
Intellectual Property.  All licensing and similar agreements relating to the
Intellectual Property are listed on Schedule 4.11 of the Schedule of Exceptions
and are in full force and effect, and there is no default by the Corporation or
any other party to such agreements.  The Corporation has not received notice of
conflict with the asserted rights of other Persons.  To its best knowledge, the
Corporation is not infringing any patents, trademarks or copyrights and is not
misappropriating or violating trade secrets or other proprietary rights of any
other Persons.  All executive officers of the Corporation have executed an
agreement containing an assignment of inventions provision, a form of which has
been provided to counsel for the Series E Investors.

          4.12.  Environmental Matters.  The Corporation is in compliance with
                 ---------------------
applicable Environmental Laws.  To the Corporation's best knowledge, there is no
past or existing event, condition, circumstance or practice or procedure
involving or relating to Hazardous Materials or other environmental matters
which might interfere with or adversely affect the conduct of the Business as
now being conducted, or which would require disclosure, reporting, monitoring,
cleanup, remediation or other action on the part of the Corporation or at the
Corporation's expense, or which might result in the Corporation's being in
violation of or in noncompliance with Environmental Laws.

          4.13.  Employees.  Employees of the Business are employed "at will",
                 ---------
and, except as otherwise provided in this Agreement, the employment of each
employee may be terminated at any time, without obligation to pay severance or
other payments or benefits.  None of the Corporation's employees are represented
by any labor union or other organization and, there have been no attempts by or
on behalf of the Corporation's employees to be represented by a labor union.
There are no controversies pending or, to the Corporation's best knowledge,
threatened between the Corporation and its employees or consultants, present or
former.  The Corporation considers its relations with employees to be good.
Schedule 4.13 of the Schedule of Exceptions also contains a complete and correct
list, as of the date of this Agreement, of all bonus, deferred compensation,
severance, pension, profit-sharing, retirement, insurance, stock purchase, stock
option and other fringe benefit plans, written or otherwise, maintained or
sponsored by the
<PAGE>

                                      -9-

Corporation in which employees or former employees of the Business are eligible
to participate.

          4.14.  Undisclosed Liabilities. To the Corporation's best knowledge,
                 -----------------------
neither the Corporation nor the Business is liable for or subject to any
material Liabilities, except material Liabilities adequately and specifically
disclosed or reserved for in the Financial Statements or, if incurred subsequent
to the date of the Corporation's balance sheet included in the Financial
Statements, disclosed and adequately reserved for in the Books and Records.

          4.15.  Books of Accounts; Returns and Reports; Taxes. The Corporation
                 ---------------------------------------------
has paid in full all taxes which were due and payable to date, and the Books and
Records reflect appropriate accruals and reserves for taxes in respect of
current periods which are not yet due and payable. The Corporation has duly and
timely filed all tax returns required to have been filed to date in all
applicable jurisdictions with respect to the Business or otherwise, except where
the failure to so file would not have a material adverse effect on the
Corporation. The Corporation has made all deposits required with respect to
withholding taxes for employees of the Business.

          4.16.  Transactions With Affiliates. The Corporation has no
                 ----------------------------
outstanding contract, agreement or other arrangement with an Affiliate of the
Corporation with respect to the Business, and none of the Corporation's assets
is owned by or leased, licensed or otherwise used by the Corporation under grant
from any of such Affiliate. There are currently no outstanding shareholder notes
or obligations to related parties of the Corporation.

          4.17.  Broker's or Finder's Fees. No broker, finder or other Person
                 -------------------------
acting in a similar capacity, other than Credit Suisse First Boston, has acted
directly or indirectly for the Corporation in connection with this Agreement or
the transactions contemplated by this Agreement.

          4.18.  Year 2000. Any reprogramming required to permit the proper
                 ---------
functioning, in and following the year 2000, of the Corporation's internal
computer systems and equipment containing embedded microchips used in the
Corporation's business, and the testing of all such systems and equipment, as so
reprogrammed, has been completed. The cost to the Corporation of such
reprogramming and testing and the reasonably foreseeable consequences of year
2000 to the Corporation will not have a material adverse effect on the
Corporation.

          4.19.  No Misleading Statements. To the Corporation's knowledge, none
                 ------------------------
of this Agreement, the Shareholders' Agreement, the Registration Rights
Agreement or any certificate furnished to the Series E Investors in connection
herewith (when read together) contain any untrue statement of material fact or
omit to state any material fact necessary to make the statements contained
herein or therein not misleading in any material respect.
<PAGE>

                                      -10-

     5.   REPRESENTATIONS AND WARRANTIES OF THE SERIES E INVESTORS. Each of the
          --------------------------------------------------------
Series E Investors makes the following representations and warranties to the
Corporation, severally and not jointly, and each with respect only to itself,
himself or herself:

          5.1.  Organization and Authority. Such Series E Investor, if not a
                --------------------------
natural person, is duly organized, validly existing and in good standing under
the laws of its jurisdiction of formation. Such Series E Investor has full power
and authority to enter into this Agreement and to perform its, his or her
obligations under this Agreement. The signing, delivery and performance of this
Agreement, the Shareholders' Agreement and the Registration Rights Agreement by
such Series E Investor have been duly authorized by all necessary action on the
part of such Series E Investor, and no further action is required on the part of
such Series E Investor in order to authorize this Agreement, the Shareholders'
Agreement, the Registration Rights Agreement or the transactions contemplated
hereby or thereby. Each of this Agreement, the Shareholders' Agreement and the
Registration Rights Agreement constitute the legal, valid and binding obligation
of such Series E Investor, duly enforceable against such Series E Investor in
accordance with its terms.

          5.2.  No Conflict or Violation. Neither the execution and delivery of
                ------------------------
this Agreement, the Shareholders' Agreement or the Registration Rights Agreement
by such Series E Investor nor the performance by such Series E Investor of the
transactions contemplated hereby or thereby will result in: (i) a violation of
or conflict with the governing documents of such Series E Investor, if not a
natural person; (ii) a violation of any Laws or any Order to which such Series E
Investor is subject; or (iii) a breach or default under any mortgage, indenture,
deed of trust, real property or personal property lease, license, contract or
other agreement to which such Series E Investor is subject.

          5.3.  Consents and Approvals. The execution, delivery and performance
                ----------------------
by such Series E Investor of this Agreement, the Shareholders' Agreement and the
Registration Rights Agreement and the transactions contemplated hereby and
thereby do not require the consent, approval or authorization of, or any
declaration, filing, registration or notice with or to any governmental or
regulatory or any other Person other than such consents or approvals which have
been obtained prior to the date of this Agreement.

          5.4.  Purchase for Investment. (a) Such Series E Investor has
                -----------------------
substantial experience in evaluating and investing in private placement
transactions of securities in companies similar to the Corporation such that
such Series E Investor is capable of evaluating the merits and risks of its
investment in the Corporation and has the capacity to protect its own interests.
Such Series E Investor is an "accredited investor" as that term is defined in
Rule 501 promulgated under the Securities Act of 1933.

          (b) Such Series E Investor is acquiring the Series E Shares for
investment, for such Series E Investor's own account, not as a nominee or agent,
and not with the view to, or for resale in connection with, any distribution
thereof. Such Series E Investor
<PAGE>

                                      -11-

understands that the Series E Shares and Common Stock issuable upon conversion
thereof have not been, and will not be when issued, registered under the
Securities Act of 1933 and are being issued pursuant to a specific exemption
from the registration provisions of the Securities Act of 1933, the availability
of which depends upon, among other things, the bona fide nature of the
investment intent and the accuracy of the representations as expressed herein.

          (c) Such Series E Investor acknowledges that the Series E Shares and
the Common Stock issuable upon conversion thereof must be held indefinitely
unless subsequently registered under the Securities Act of 1933 or unless an
exemption from such registration is available.  Such Series E Investor is aware
of the provisions of Rule 144 promulgated under the Securities Act of 1933 which
permit limited resale of shares purchased in a private placement subject to the
satisfaction of certain conditions.

          (d) Such Series E Investor understands that no public market now
exits, and that a market may never exist, for any of the securities issued by
the Corporation.

          5.5.  Broker's or Finder's Fees.  No broker, finder or other Persons
                -------------------------
acting in a similar capacity has acted directly or indirectly for such Series E
Investor in connection with this Agreement and the transactions contemplated
hereby.

     6.   POST-CLOSING COVENANT OF THE CORPORATION.
          ----------------------------------------

          6.1.  Insurance.  The Corporation shall keep in full force and effect,
                ---------
and shall pay all premiums on, a term life insurance policy on the life of
Joseph Beninati in the amount of $5,000,000 as to which the Corporation shall be
the owner and the beneficiary.  The Corporation shall keep in full force and
effect, and shall pay all premiums on, a Directors and Officers liability
insurance policy in the amount of at least $1,000,000 as to which the
Corporation shall be the owner and the beneficiary.  The Corporation shall
increase such amount to at least $5,000,000 prior to the Corporation's Initial
Public Offering.

     7.   CLOSING DELIVERIES
          ------------------

          7.1.  The Corporation's Closing Deliveries for the Initial Closing.
                ------------------------------------------------------------
The participating Series E Investors' obligations to purchase the Series E
Shares at the Initial Closing are subject to the fulfillment by the Corporation
or waiver by the participating Series E Investors of the following conditions at
the Initial Closing:

                7.1.1.  The representations and warranties made by the
Corporation in Section 4 hereof shall be true and correct as of the Initial
Closing.

                7.1.2.  All covenants, agreements and conditions contained in
this Agreement to be performed by the Corporation on or prior to the Initial
Closing shall have been performed or complied with unless waived in writing by
the Series E Investors purchasing Series E Shares at the Initial Closing.
<PAGE>

                                      -12-

               7.1.3.  The Corporation shall have obtained all necessary state
securities law permits and qualifications, or have the availability of
exemptions therefrom, required by any state for the offer and sale of Series E
Shares and the Common Stock issuable upon conversion of the Series E Shares.

               7.1.4.  The Third Amended and Restated Certificate of
Incorporation of the Corporation shall have been filed with the Secretary of
State of the State of Delaware.

               7.1.5.  The Corporation shall deliver a certificate executed by
the Chief Executive Officer of the Corporation, dated as of the Initial Closing,
certifying that the conditions specified in Sections 7.1.1, 7.1.2 and 7.1.4 of
this Agreement have been fulfilled.

               7.1.6.  The Corporation shall deliver a certificate dated as of
the date of the Initial Closing, of the Secretary of the Corporation certifying
as to (i) the certificate of incorporation and bylaws of the Corporation; and
(ii) resolutions of the Board of Directors and the shareholders of the
Corporation authorizing the execution, delivery and performance of this
Agreement, all documents contemplated by this Agreement and the transactions
contemplated by this Agreement.

               7.1.7.  The Corporation shall deliver certificates of "good
standing" of the Corporation from the Secretaries of State of the States of
Delaware, Connecticut, New York, New Jersey and the Commonwealth of
Massachusetts.

               7.1.8.  The Corporation shall deliver stock certificates issued
to the participating Series E Investors for the number of Series E Shares set
forth on the Schedule of Investors.

               7.1.9.  The Corporation shall deliver the Shareholders' Agreement
signed on behalf of the Corporation and by or on behalf of the holders of the
Series A Shares, Series B Shares, Series C Shares and Series D Shares.

               7.1.10. The Corporation shall deliver the Registration Rights
Agreement signed on behalf of the Corporation.

               7.1.11. The Corporation shall deliver an opinion of Testa,
Hurwitz & Thibeault, LLP, counsel to the Corporation in the form attached hereto
as Exhibit C.
   ---------

        7.2. Closing Deliveries of the Series E Investors for the Initial
             ------------------------------------------------------------
Closing.  The Corporation's obligations to sell and issue the Series E Shares at
-------
the Initial Closing are subject to the fulfillment by the participating Series E
Investors or waiver by Corporation of the following conditions:

               7.2.1.  The participating Series E Investors shall deliver to the
Corporation the sum set forth opposite its, his or her name in the Schedule of
Investors,
<PAGE>

                                      -13-

by wire transfer, representing the purchase price of the Series E Shares to be
issued pursuant to this Agreement.

               7.2.2.  Each participating Series E Investor shall deliver to the
Corporation the Shareholders' Agreement signed by such Series E Investor.

               7.2.3.  Each Series E Investor shall deliver to the Corporation
the Registration Rights Agreement signed by such Series E Investor.

        7.3. The Corporation's Closing Deliveries for the Additional Closing.
             ---------------------------------------------------------------
The participating Series E Investors' obligations to purchase the Series E
Shares at the Additional Closing are subject to the fulfillment by the
Corporation or waiver by the participating Series E Investors of the following
conditions at the Additional Closing:

               7.3.1.  The representations and warranties made by the
Corporation in Section 4 hereof shall be true and correct as of the Additional
Closing.

               7.3.2.  All covenants, agreements and conditions contained in
this Agreement to be performed by the Corporation on or prior to the Additional
Closing shall have been performed or complied with unless waived in writing by
the Series E Investors purchasing Series E Shares at the Additional Closing.

               7.3.3.  The Corporation shall have obtained all necessary state
securities law permits and qualifications, or have the availability of
exemptions therefrom, required by any state for the offer and sale of Series E
Shares and the Common Stock issuable upon conversion of the Series E Shares.

               7.3.4.  The Third Amended and Restated Certificate of
Incorporation of the Corporation shall have been filed with the Secretary of
State of the State of Delaware.

               7.3.5.  The Corporation shall deliver a certificate executed by
the Chief Executive Officer of the Corporation, dated as of the Additional
Closing, certifying that the conditions specified in Sections 7.3.1, 7.3.2 and
7.3.4 of this Agreement have been fulfilled.

               7.3.6.  The Corporation shall deliver a certificate dated as of
the date of the Additional Closing, of the Secretary of the Corporation
certifying as to (i) the certificate of incorporation and bylaws of the
Corporation; and (ii) resolutions of the Board of Directors and the shareholders
of the Corporation authorizing the execution, delivery and performance of this
Agreement, all documents contemplated by this Agreement and the transactions
contemplated by this Agreement.

               7.3.7.  The Corporation shall deliver certificates of "good
standing" of the Corporation from the Secretaries of State of the States of
Delaware, Connecticut, New York, New Jersey and the Commonwealth of
Massachusetts.
<PAGE>

                                      -14-

                7.3.8.  The Corporation shall deliver stock certificates issued
to the participating Series E Investors for the number of Series E Shares set
forth on the Schedule of Investors.

                7.3.9.  The Corporation shall deliver the Shareholders'
Agreement signed on behalf of the Corporation and by or on behalf of the holders
of the Series A Shares, Series B Shares, Series C Shares and Series D Shares.

                7.3.10. The Corporation shall deliver the Registration Rights
Agreement signed on behalf of the Corporation.

                7.3.11. The Corporation shall deliver an opinion of Testa,
Hurwitz & Thibeault, LLP, counsel to the Corporation in the form attached hereto
as Exhibit C.
   ---------

          7.4. Closing Deliveries of the Series E Investors for the Additional
               ---------------------------------------------------------------
Closing.  The Corporation's obligations to sell and issue the Series E Shares at
-------
the Additional Closing are subject to the fulfillment by the participating
Series E Investors or waiver by Corporation of the following conditions:

                7.4.1.  The participating Series E Investors shall deliver to
the Corporation the sum set forth opposite its, his or her name in the Schedule
of Investors, by wire transfer, representing the purchase price of the Series E
Shares to be issued pursuant to this Agreement.

                7.4.2.  Each participating Series E Investor shall deliver to
the Corporation the counterpart signature page to the Shareholders' Agreement
signed by such Series E Investor.

                7.4.3.  Each Series E Investor shall deliver to the Corporation
the counterpart signature page to the Registration Rights Agreement signed by
such Series E Investor.

     8. SURVIVAL OF REPRESENTATIONS, WARRANTIES AND COVENANTS.  All covenants,
        -----------------------------------------------------
representations and warranties in this Agreement or in any documents delivered
pursuant to this Agreement (A) (other than those in Section 4.1 and 4.2) shall
survive the Closing for a period of 1 (one) year after the Closing and (B)
contained in Sections 4.1 and 4.2 only shall survive the Closing for a period of
3 (three) years after the Closing.

     9. INDEMNIFICATION.
        ---------------

          9.1. Indemnification by the Corporation to the Series E Investors.
               ------------------------------------------------------------
The Corporation shall indemnify, defend and hold each of the Series E Investors,
the Affiliates of each Series E Investor, and their respective shareholders,
officers, directors, employees, assignees and successors, harmless against, and
shall reimburse each of the indemnified Persons on demand on account of, any
Losses which may be asserted against, imposed on or incurred by any of them as a
result of or arising out of or in any manner
<PAGE>

                                      -15-

relating or attributable to any inaccuracy in or breach of the representations,
warranties or covenants on the part of the Corporation in this Agreement or in
any document delivered by the Corporation pursuant to this Agreement.

          9.2.  Indemnification by the Series E Investors to the Corporation.
                ------------------------------------------------------------
Each Series E Investor, severally and not jointly, shall indemnify, defend and
hold the Corporation and the Corporation's officers, directors, employees,
assignees and successors harmless against, and shall reimburse such indemnified
Persons on demand on account of, any Losses which may be asserted against,
imposed on or incurred by any of them as a result of or arising out of or in any
manner relating or attributable to any inaccuracy in or breach of such Series E
Investor's representations or warranties in this Agreement or in any document
delivered by such Series E Investor pursuant to this Agreement; provided
however, such obligation shall not exceed the amount the purchase price paid by
such Series E Investor for the Series E Shares as set forth on the Schedule of
Investors.

     10. MISCELLANEOUS.
         -------------

          10.1. Notices.  Notices given pursuant to this Agreement must be in
                -------
writing.  They shall be deemed to have been duly given:  (i) upon delivery or
refusal to accept delivery, if hand-delivered; (ii) when transmitted, if sent by
fax with confirmed receipt, followed by a "hard" copy delivered by any other
method specified in this Section 10.1; or (iii) one (1) business day after being
deposited for next-day delivery with Federal Express or other national overnight
courier service.  In each case, notice shall be addressed to the parties as
follows:

          If to the Corporation:
          ---------------------

                Greenwich Technology Partners, Inc.
                43 Gate House Road
                Stamford, Connecticut 06902
                Attention:  Dennis M. Goett
                Fax: (203) 969-1500

          If to the Series E Investors:
          ----------------------------

          To the address of such Series E Investor as set forth on the Schedule
          of Investors

or to such other place and with such other concurrent copies as the parties may
subsequently designate by written notice.

          10.2. Amendment; Waiver.  None of the provisions of this Agreement may
                -----------------
be changed, modified, waived or canceled orally or otherwise except in writing,
signed by the Corporation and persons holding at least 66 2/3% of the then
outstanding
<PAGE>

                                      -16-

Series E Shares (assuming conversion to Common Stock at the conversion rate then
in effect).

          10.3.  Binding Effect; Assignment.  This Agreement is binding on the
                 --------------------------
Corporation, the Series E Investors and their respective successors in interest.
No party may assign his or its rights and obligations under this Agreement
without the prior written consent of the other parties.  There are no third-
party beneficiaries of this Agreement, and any intention to afford any right or
benefit under this Agreement to any third party is specifically disclaimed.

          10.4.  Entire Agreement.  This Agreement, including the exhibits
                 ----------------
attached hereto, the Shareholders' Agreement and the Registration Rights
Agreement embody the entire understanding among the parties with respect to the
subject matter of this Agreement.  There are no binding agreements or
understandings among the parties with respect to the transactions contemplated
by this Agreement other than as expressly set forth in this Agreement, the
Shareholders' Agreement or the Registration Rights Agreement.

          10.5.  Interpretation; Construction.
                 ----------------------------

                  10.5.1.  The terms of this Agreement have been fully
negotiated by the parties in consultation with counsel, and the wording of this
Agreement has been arrived at by all of them as a result of their joint
discussions. Accordingly, no provision of this Agreement shall be construed
against a particular party or in favor of another party merely because of which
party (or its representatives) drafted or supplied the wording for such
provision.

                  10.5.2.  Except where otherwise noted in context, all
references to "Sections", "Exhibits" or "Schedules" shall be deemed to refer to
the sections or subsections, as appropriate, exhibits or schedules of this
Agreement.

                  10.5.3.  Section headings appearing in this Agreement are
inserted solely as reference aids for the ease and convenience of the reader;
they shall not be deemed to modify, limit or define the scope or substance of
the provisions they introduce, nor shall they be used in construing the intent
or effect of such provisions.

                  10.5.4.  Where the context requires: (i) use of the singular
or plural incorporates the other, and (ii) pronouns and modifiers in the
masculine, feminine or neuter gender shall be deemed to refer to or include the
other genders.

                  10.5.5.  As used in this Agreement, the terms "include(s)" and
"including" mean "including but not limited to"; that is each case the example
or enumeration which follows the use of either term is illustrative but no
exclusive or exhaustive.

          10.6.  Expenses.  The Corporation shall pay (or reimburse the Series E
                 --------
Investors for, as the case may be) the reasonable out-of-pocket fees and
disbursements of
<PAGE>

                                      -17-

the Series E Investors incurred in connection with the negotiation and
consummation of the transactions contemplated hereby, including attorney and
consulting fees and disbursements incurred by a single counsel on behalf of the
Series E Investors, in an aggregate amount not to exceed $20,000.

          10.7.  Multiple Counterparts.  This Agreement may be signed in one or
                 ---------------------
more counterparts, each of which shall be deemed to be an original and all of
which shall be considered one and the same agreement and shall become effective
when each of the parties has signed and delivered a counterpart to the other.

          10.8.  Further Assurances.  The parties agree, upon request and for no
                 ------------------
additional consideration, to sign, acknowledge and deliver any documents and to
do anything else which the other may reasonably request in order to carry out
more completely the purpose and intent of this Agreement consistent with its
terms.

          10.9.  Governing Law.  This Agreement shall be governed by and
                 -------------
interpreted according to the Laws of the State of Delaware, but without giving
effect to any Delaware choice of law provisions which might otherwise make the
Laws of a different jurisdiction govern or apply.

                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]
<PAGE>

     IN WITNESS WHEREOF, the Corporation and the participating Series E
Investors have executed this Agreement as of the day and year first above
written.

                                       Greenwich Technology Partners, Inc.

                                       /s/ Dennis M. Goett
                                           -------------------------------------
                                            Name:
                                            Title:
<PAGE>

SERIES E INVESTOR:

CHASE VENTURE CAPITAL ASSOCIATES, L.P.

/s/ Stephen Murray
    -----------------------------
     its General Partner

By:______________________________
<PAGE>

SERIES E INVESTOR:

CREDIT SUISSE FIRST BOSTON VENTURE FUND I, L.P.

By: QBB MANAGEMENT FUND I, LLC,
    its General Partner

/s/ William J.B. Brady III
    ----------------------
<PAGE>

SERIES E INVESTOR:

FG-GTPF

/s/ Kathleen E. Shepphird
    ---------------------------
Name: Kathleen E. Shepphird
Title: Managing Director
<PAGE>

SERIES E INVESTOR:

STV PARTNERS III, L.L.C.


By: Jerome C. Silvey,
    its General Manager


/s/ Jerome C. Silvey
    ----------------------------
<PAGE>

SERIES E INVESTOR:

WHEATLEY PARTNERS II L.P.


/s/ Irwin Lieber
    ----------------------------
     Irwin Lieber
     General Partner
<PAGE>

SERIES E INVESTOR:

VANTAGEPOINT VENTURE PARTNERS 1996


By:  VantagePoint Associates, LLC,
     its General Partner


/s/ James D. Marver
    ----------------------------
     Name: James D. Marver
     Title: Managing Member
<PAGE>

SERIES E INVESTOR:

VANTAGEPOINT COMMUNICATIONS
 PARTNERS, LP


By:  VantagePoint Communications Associates, LLC,
     its General Partner


/s/ James D. Marver
    ----------------------------
     Name: James D. Marver
     Title: Managing Member
<PAGE>

                              /s/ Edwin J. O'Mara
                                  -------------------------------
                              Name: Edwin J. O'Mara
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/13/99
                                     ----------------------------




                              /s/ John Stopper
                                  -------------------------------
                              Name: John Stopper
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/20/99
                                     ----------------------------




                              /s/ Laurence Pinkus
                                  -------------------------------
                              Name: Laurence Pinkus
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/11/99
                                     ----------------------------




                              /s/ Kevin Bock
                                  -------------------------------
                              Name: Kevin Bock
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/18/99
                                     ----------------------------



                              /s/ James Tucci
                                  -------------------------------
                              Name: James Tucci
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/18/99
                                     ----------------------------
<PAGE>

                              /s/ Robert Berlin
                                  -------------------------------
                              Name: Robert Berlin
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/11/99
                                     ----------------------------




                              /s/ John V. Wheeler
                                  -------------------------------
                              Name: John V. Wheeler
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/13/99
                                     ----------------------------



                              /s/ L. David Cardenas
                                  -------------------------------
                              Name: L. David Cardenas
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/11/99
                                     ----------------------------



                              /s/ Louis J. Mischianti
                                  -------------------------------
                              Name: Louis J. Mischianti
                                    -----------------------------
                              Title:_____________________________

                              Date:______________________________




                              /s/ James A. Conroy
                                  -------------------------------
                              Name: James A. Conroy
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/11/99
                                     ----------------------------
<PAGE>

                              /s/ Emil Roymans
                                  -------------------------------
                              Name: Emil Roymans
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/15/99
                                     ----------------------------


                              /s/ Paul A. Rubin
                                  -------------------------------
                              Name: Paul A. Rubin
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/11/99
                                     ----------------------------


                              /s/ Scott M. Freeman
                                  -------------------------------
                              Name: Scott M. Freeman
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/12/99
                                     ----------------------------



                              /s/ Michael J. Schmidtberger
                                  -------------------------------
                              Name: Michael J. Schmidtberger
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/12/99
                                     ----------------------------



                              /s/ Michael Grossman
                                  -------------------------------
                              Name: Michael Grossman
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/14/99
                                     ----------------------------



                              /s/ Karl Frey
                                  -------------------------------
                              Name: Karl Frey
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/11/99
                                     ----------------------------
<PAGE>

                              EPFL Partners

                              /s/ Russell Carpenteri
                                  -------------------------------
                              Name: Russell Carpenteri
                                    -----------------------------
                              Title: Partner
                                     ----------------------------

                              Date:  10/12/99
                                     ----------------------------


                              /s/ John D. Miller
                                  -------------------------------
                              Name: John D. Miller
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/14/99
                                     ----------------------------



                              /s/ Deborah A. Farrington
                                  -------------------------------
                              Name: Deborah A. Farrington
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/14/99
                                     ----------------------------
<PAGE>

                        /s/ Gerard F. Becker and Christine B. Becker
                           ----------------------------------------------
                        Name: Gerard F. Becker and Christine B. Becker
                              -------------------------------------------
                        Title:___________________________________________

                        Date:  10/13/99
                               ------------------------------------------


                        /s/ Nicholas A. Johnson and Patricia A. Johnson
                            ---------------------------------------------
                        Name: Nicholas A. Johnson and Patricia A. Johnson
                              -------------------------------------------
                        Title:___________________________________________

                        Date:  11/29/99
                               ------------------------------------------



                              Clemente Family Trust


                              /s/ Richard Clemente
                                  ---------------------------------------
                              Name: Richard Clemente
                                    -------------------------------------
                              Title: Trustee
                                     ------------------------------------

                              Date:  10/13/99
                                     ------------------------------------


                              BMZ Investments

                              /s/ Stacey Cox
                                  ---------------------------------------
                              Name: Stacey E. Cox
                                    -------------------------------------
                              Title: Partner
                                     ------------------------------------

                              Date:  10/13/99
                                     ------------------------------------



                              /s/ Richard J. Testa
                                  ---------------------------------------
                              Name: Richard J. Testa
                                    -------------------------------------
                              Title:_____________________________________

                              Date:______________________________________
<PAGE>

                              /s/ Anthony M. Carvette
                                  -------------------------------
                              Name: Anthony M. Carvette
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/20/99
                                     ----------------------------



                              /s/ Greg Berger
                                  -------------------------------
                              Name: Greg Berger
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/15/99
                                     ----------------------------



                              /s/ Kevin J. Kitson
                                  -------------------------------
                              Name: Kevin J. Kitson
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/11/99
                                     ----------------------------



                              /s/ Brian J. Flynn
                                  -------------------------------
                              Name: Brian J. Flynn
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/12/99
                                     ----------------------------



                              /s/ Angus M. Green
                                  -------------------------------
                              Name: Angus M. Green
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/13/99
                                     ----------------------------



                              /s/ Joseph A. Cabrera
                                  -------------------------------
                              Name: Joseph A. Cabrera
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/14/99
                                     ----------------------------
<PAGE>

                              /s/ Clint Heiden
                                  -------------------------------
                              Name: Clint Heiden
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/16/99
                                     ----------------------------



                              /s/ Stephen B. Seigel
                                  -------------------------------
                              Name: Stephen B. Seigel
                                    -----------------------------
                              Title:_____________________________

                              Date:______________________________



                              /s/ DHW Turner
                                  -------------------------------
                              Name: DHW Turner
                                    -----------------------------
                              Title:_____________________________

                              Date:  10/22/99
                                     ----------------------------



                              /s/ Dennis M. Goett
                                  -------------------------------
                              Name: Dennis M. Goett
                                    -----------------------------
                              Title:_____________________________

                              Date:______________________________

                              IRA f/b/o Dennis M. Goett

                              /s/ Dennis M. Goett
                                  -------------------------------
                              Name:______________________________
                              Title:_____________________________

                              Date:  10/11/99
                                     ----------------------------
<PAGE>

                         /s/ S. Elizabeth Press and Mark Andrew Mohn
                             ---------------------------------------
                         Name: Elizabeth Press and Mark Andrew Mohn
                               -------------------------------------
                         Title:_____________________________________

                         Date:  10/13/99
                                ------------------------------------



                              /s/ Paul C. Carey
                                  ----------------------------------
                              Name: Paul C. Carey
                                    --------------------------------
                              Title:________________________________

                              Date:  10/13/99
                                     -------------------------------



                              /s/ Samer Tawfik
                                  ----------------------------------
                              Name: Samer Tawfik
                                    --------------------------------
                              Title:________________________________

                              Date:  10/14/99
                                     -------------------------------



                              HIGHWOOD PARTNERS LLC


                              /s/ Ari Horowitz
                                  ----------------------------------
                              Name: Ari Horowitz
                                    --------------------------------
                              Title: CEO
                                     -------------------------------

                              Date:  10/14/99
                                     -------------------------------



                              /s/ William Cox and Beatrice Cox
                                  ----------------------------------
                              Name: William Cox and Beatrice Cox
                                    --------------------------------
                              Title:________________________________

                              Date:  10/15/99
                                     -------------------------------
<PAGE>

                              /s/ Gregory W. Carney
                                  ------------------------------------
                              Name: Gregory W. Carney
                                    ----------------------------------
                              Title:__________________________________

                              Date:  10/15/99
                                     ---------------------------------



                              /s/ Paul T. Goldman
                                  ------------------------------------
                              Name: Paul T. Goldman
                                    ----------------------------------
                              Title:__________________________________

                              Date:  10/15/99
                                     ---------------------------------




                              /s/ Donald K. Bryan and Belinda B. Bryan
                                  ------------------------------------
                              Name: Donald K. Bryan
                                    ----------------------------------
                              Title:__________________________________

                              Date:  10/14/99
                                     ---------------------------------



                              /s/ Edward Cettina
                                  ------------------------------------
                              Name: Edward Cettina
                                    ----------------------------------
                              Title:__________________________________

                              Date:  10/17/99
                                     ---------------------------------



                              /s/ Elio Cettina
                                  ------------------------------------
                              Name: Elio Cettina
                                    ----------------------------------
                              Title:__________________________________

                              Date:  10/18/99
                                     ---------------------------------
<PAGE>

                              The CIT Group/Equity Investments, Inc.

                              /s/ Mark Vander Veen
                                  ------------------------------------
                              Name: Mark Vander Veen
                                   -----------------------------------
                              Title: Vice President
                                     ---------------------------------

                              Date:  10/27/99
                                     ---------------------------------

                              Chase Venture Capital Associates L.P.

                              /s/ Donald J. Hofmann
                                  ------------------------------------
                              Name: Donald J. Hofmann
                                    ----------------------------------
                              Title: General Partner
                                     ---------------------------------

                              Date:  10/19/99
                                     ---------------------------------


                       VantagePoint Communications Partners, L.P.
                       By: VantagePoint Communications Associate, L.L.C.,
                           Its General Partner

                       /s/ James D. Marver
                           -------------------------------------------
                       Name: James D. Marver
                             -----------------------------------------
                       Title:  Managing Member
                               ---------------------------------------


                              VantagePoint Venture Partners 1996, L.P.
                              By: VantagePoint Associates, L.L.C.,
                                  Its General Partner

                              /s/ James D. Marver
                                  ------------------------------------
                              Name: James D. Marver
                                    ----------------------------------
                              Title: Managing Director
                                     ---------------------------------



                              /s/ Mark B. Templeton
                                  ------------------------------------
                              Name: Mark B. Templeton
                                    ----------------------------------
                              Title:__________________________________

                              Date:  12/30/99
                                     ---------------------------------
<PAGE>

                              /s/ Mark Wolfenberger
                                  ------------------------------------
                              Name: Mark Wolfenberger
                                    ----------------------------------
                              Title:__________________________________

                              Date:  01/03/00
                                     ---------------------------------



                              /s/ Frank P. Slattery
                                  ------------------------------------
                              Name: Frank P. Slattery
                                    ----------------------------------
                              Title:__________________________________

                              Date:  12/30/99
                                     ---------------------------------



                              /s/ Jeffrey A. Wrona
                                  ------------------------------------
                              Name: Jeffrey A. Wrona
                                    ----------------------------------
                              Title:__________________________________

                              Date:  01/04/00
                                     ---------------------------------



                              /s/ Michael K. Ma
                                  ------------------------------------
                              Name: Michael K. Ma
                                    ----------------------------------
                              Title:__________________________________

                              Date:  01/03/99
                                     ---------------------------------


                              /s/ Kurt Weber
                                  ------------------------------------
                              Name: Kurt Weber
                                    ----------------------------------
                              Title:__________________________________

                              Date:  12/31/99
                                     ---------------------------------

                              UGE Enterprises LLC

                              /s/ Roger Cozzi
                                  ------------------------------------
                              Name: Roger Cozzi
                                    ----------------------------------
                              Title: Partner
                                     ---------------------------------

                              Date:  01/06/00
                                     ---------------------------------
<PAGE>

                              Edgell Street Partners

                              /s/ James Harasimowicz
                                  ------------------------------------
                              Name: James Harasimowicz
                                    ----------------------------------
                              Title: Managing Partner
                                     ---------------------------------

                              Date:  01/12/00
                                     ---------------------------------



                              /s/ Dennis M. Goett
                                  ------------------------------------
                              Name: Dennis M. Goett
                                    ----------------------------------
                              Title:__________________________________

                              Date:  12/30/99
                                     ---------------------------------



                              /s/ Jill Catania
                                  ------------------------------------
                              Name: Jill Catania
                                    ----------------------------------
                              Title:__________________________________

                              Date:  12/30/99
                                     ---------------------------------


                              /s/ Geryl W. Darington
                                  ------------------------------------
                              Name: Geryl W. Darington
                                    ----------------------------------
                              Title:__________________________________

                              Date:  12/31/99
                                     ---------------------------------


                              /s/ Robert J. Garbarino
                                  ------------------------------------
                              Name: Robert J. Garbarino
                                    ----------------------------------
                              Title:__________________________________

                              Date:  12/30/99
                                     ---------------------------------


                              /s/ Don Henderson
                                  ------------------------------------
                              Name: Don Henderson
                                    ----------------------------------
                              Title:__________________________________

                              Date:  01/03/00
                                     ---------------------------------
<PAGE>

                              /s/ Bruce M. Tanis
                                  ------------------------------------
                              Name: Bruce M. Tanis
                                    ----------------------------------
                              Title:__________________________________

                              Date:  12/31/99
                                     ---------------------------------



                              /s/ Peter Cherasia
                                  ------------------------------------
                              Name: Peter Cherasia
                                    ----------------------------------
                              Title:__________________________________

                              Date:  01/06/00
                                     ---------------------------------



                              /s/ Michael A. Tunstall
                                  ------------------------------------
                              Name: Michael A. Tunstall
                                    ----------------------------------
                              Title:__________________________________

                              Date:  01/03/00
                                     ---------------------------------



                              /s/ Wayne A. Segal
                                  ------------------------------------
                              Name: Wayne A. Segal
                                    ----------------------------------
                              Title:__________________________________

                              Date:  01/04/00
                                     ---------------------------------


                              /s/ Tony Trousset
                                  ------------------------------------
                              Name: Tony Trousset
                                    ----------------------------------
                              Title:__________________________________

                              Date:  01/04/00
                                     ---------------------------------


                         /s/ S. Elizabeth Press and Mark Andrew Mohn
                             -----------------------------------------
                         Name: Elizabeth Press and Mark Andrew Mohn
                               ---------------------------------------
                         Title:_______________________________________

                         Date:  01/05/00
                                --------------------------------------
<PAGE>

                              /s/ Richard Haverly
                                 -------------------------------------
                              Name: Richard Haverly
                                    ----------------------------------
                              Title:__________________________________

                              Date:___________________________________


                              HIGH STREET INVESTORS 2000
                              By: Testa, Hurwitz & Thibeault, LLP

                              /s/ George W. Thibeault
                                  ------------------------------------
                              Name: George W. Thibeault
                                    ----------------------------------
                              Title: Partner
                                     ---------------------------------

                              Date:  01/14/00
                                     ---------------------------------


                              /s/ Kevin M. Barry
                                  ------------------------------------
                              Name: Kevin M. Barry
                                    ----------------------------------
                              Title:__________________________________

                              Date:  01/14/00
                                     ---------------------------------
<PAGE>

                                   EXHIBIT A
                                   ---------

                                Initial Closing
                                ---------------

<TABLE>
<CAPTION>
                    Name of Series E Investor        Registrable Securities
                    -------------------------     ----------------------------
<S>                                               <C>
Chase Venture Capital Associates, L.P.                      4,739,337
Credit Suisse First Boston Venture Fund I, L.P.               236,967
STV Partners III, L.L.C.                                      473,934
FG-GTPF                                                       236,967
Vantagepoint Communications Partners, LP                      947,867
Vantagepoint Venture Partners 1996, L.P.                      473,934
Wheatley Partners II L.P.                                     473,934
</TABLE>


                           First Additional Closing
                           ------------------------

<TABLE>
<CAPTION>
                 Name of Series E Investor         Registrable Securities
                 -------------------------      -----------------------------
<S>                                             <C>
Edwin J. O'Mara                                             7,108
John Stopper                                               23,696
Laurence Pinkus                                             4,739
Kevin Bock                                                 50,236
James Tucci                                                59,241
Robert Berlin                                              11,848
John V. Wheeler                                            11,848
L. David Cardenas and Stacey J. Cardenas                    2,369
Louis J. Mischianti                                        23,696
James A. Conroy                                             4,739
Emil A. Roymans                                             2,369
Paul A. Rubin                                               7,109
Scott M. Freeman                                            4,739
Michael J. Schmidtberger                                    4,739
Michael A. Grossman                                         5,924
Karl Frey                                                  11,848
EPFL Partners                                               4,739
John D. Miller                                             11,848
Deborah A. Farrington                                       2,369
Gerard F. Becker and Christine B. Becker                   11,848
Nils A. Johnson and Patricia A. Johnson                     9,478
Clemente Family Trust                                       9,478
BMZ Investments                                            23,696
Richard J. Testa                                            9,952
Anthony M. Carvette                                        23,696
Greg Berger                                                 5,924
</TABLE>
<PAGE>

<TABLE>
<CAPTION>
                 Name of Series E Investor         Registrable Securities
                 -------------------------      -----------------------------
<S>                                             <C>
Kevin J. Kitson                                            47,393
Brian J. Flynn                                              4,739
Angus M. Green                                             18,957
Joseph A. Cabrera                                          11,848
Clint Heiden                                               23,696
Stephen B. Seigel                                          47,393
David HW Turner                                            11,848
Dennis M. Goett                                            18,957
IRA FBO Dennis M. Goett                                    28,435
S. Elizabeth Press and Mark Andrew Mohn                    10,000
Paul C. Carey                                              18,957
Samer Tawfik                                              142,180
Highwood Partners LLC                                      14,218
William C. Cox III and Beatrice I. Cox                      9,478
Gregory W. Carney                                          11,848
Paul T. Goldman                                             7,109
Donald K. Bryan and Belinda B. Bryan                       11,848
Edward Cettina                                              7,109
Elio Cettina                                                7,109
The CIT Group/Equity Investments, Inc.                    473,934
Chase Venture Capital Associates, L.P.                    473,933
VantagePoint Venture Partners 1996, L.P.                  157,820
VantagePoint Communications Partners, L.P.                316,114
</TABLE>
<PAGE>

                           Second Additional Closing
                           -------------------------

<TABLE>
<CAPTION>
                 Name of Series E Investor         Registrable Securities
                 -------------------------      -----------------------------
<S>                                             <C>
Mark B. Templeton                                          11,848
Mark Wolfenberger                                          23,696
Frank P. Slattery                                           4,739
Jeffrey Wrona                                               4,739
Michael Ma                                                  4,739
Kurt Weber                                                 11,848
UGE Enterprises LLC                                         4,739
Edgell Street Partners                                      7,109
Dennis M. Goett                                            14,218
Jill Catania                                                4,739
Geryl Darington                                            11,848
Robert Garbarino                                           23,696
Donald Henderson                                            9,478
Bruce M. Tanis                                             11,848
Peter Cherasia                                             23,696
Michael Tunstall                                           35,545
Wayne A. Segal                                             23,696
Anthony Trousett                                           23,696
S. Elizabeth Press and Mark Andrew Mohn                    20,000
Richard Haverly                                           100,000
High Street Investors 2000                                 47,393
Kevin M. Barry                                              4,739
</TABLE>
<PAGE>

                                   EXHIBIT B
                                   ---------

                            Schedule of Exceptions

                                 See Attached

<PAGE>

                                   EXHIBIT C
                                   ---------


              Form of Opinion of Testa, Hurwitz & Thibeault, LLP