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                                                                    Exhibit 10.1


                    STOCK PURCHASE AND TERMINATION AGREEMENT



                         dated as of February 27, 1998



                                 by and between



                              NEVASA HOLDINGS LTD.
                              CORPORACION IMPSA SA
                               MILITELLO LIMITED
                       ROTLING INTERNATIONAL CORPORATION
                            RICARDO ANIBAL VERDAGUER
                           ROBERTO ABEL VIVO CHANETON
                               IMPSAT CORPORATION
                                   IMPSAT SA



                                      and



                       STET INTERNATIONAL NETHERLANDS NV


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                    STOCK PURCHASE AND TERMINATION AGREEMENT

This Stock Purchase and Termination Agreement (this "Agreement") is dated
February 27, 1998

                                 by and between

1. NEVASA HOLDINGS LTD., a corporation organized and existing under the laws of
   the Republic of Ireland ("Nevasa"), having its registered office at First
   Floor, 17 Dame Street, Dublin 2;

2. CORPORACION IMPSA SA, a corporation organized and existing under the laws of
   the Republic of Argentina ("CORIM"), having its headquarters at Av. E. Madero
   940, 19th Floor, Buenos Aires;

3. MILITELLO LIMITED, a corporation organized and existing under the laws of
   Tortola, British Virgin Islands ("Militello"), having its registered office
   at ATC Trustees (BVI) Limited, Road Town, Tortola, British Virgin Islands;

4. ROTLING INTERNATIONAL CORPORATION, a corporation organized and existing under
   the laws of Tortola, British Virgin Islands ("Rotling"), having its
   registered office at Sucre & Sucre Trust Limited, Chera Chambers, Road Town,
   Tortola, British Virgin Islands;

5. MR RICARDO ANIBAL VERDAGUER, an individual ("Verdaguer"), residing at Alferez
   Pareja 256, Buenos Aires, Argentina;

6. MR ROBERTO ABEL VIVO CHANETON, an individual ("Vivo"), residing at Alferez
   Pareja 256, Buenos Aires, Argentina;

7. IMPSAT CORPORATION., a corporation organized and existing under the laws of
   the State of Delaware, United States of America (the "Company"), having its
   headquarters at Corporation Trust Center, 209 Orange Street, Wilmington,
   Country of Newcastle, Delaware, United States of America; and

8. IMPSAT SA., a corporation organized and existing under the laws of the
   Republic of Argentina ; ("IMPSAT Argentina"), having its headquarters at
   Alferez Pareja 256, Buenos Aires.

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(CORIM, Militello, Rotling, Verdaguer and Vivo being hereinafter referred to
collectively as "Grupo A")

                                      and

STET INTERNATIONAL NETHERLANDS NV, a corporation organized and existing under
the laws of The Netherlands ("STET"), having its registered office in 3111
Strawinskylaan, 'Atrium', 6th Floor, Amsterdam.


                                  WITNESSETH:

- WHEREAS, STET is the owner of 25,198,160 SHARES, par value U.S.$1.00 per
  share, of the Class A voting common stock (the "Company Shares") of the
  Company, and of 33 SHARES, par value P$ 0.01 per share, of the Class B voting
  common stock (the "IMPSAT Shares") of IMPSAT S.A., (the Company Shares and the
  IMPSAT Shares being referred to collectively as the "Shares");

- WHEREAS, Nevasa wishes to purchase from STET, and STET wishes to sell to
  Nevasa, the Shares for an aggregate purchase price of U.S.$ 125,000,000 (one
  hundred and twenty five million Dollars) (the "Purchase Price"), in each case
  in accordance with the terms and conditions set forth in this Agreement;

- WHEREAS, Nevasa, Grupo A, and STET are parties to a Shareholders Agreement,
  dated as of December 16, 1994, as amended (the "Shareholders Agreement")
  annexed hereto as Exhibit 1 relating to the ownership of the capital stock of,
  and certain management rights in respect of, the Company;

- WHEREAS, Nevasa each Person in Grupo A and STET wish to terminate the
  Shareholders Agreement with effect from the Closing Date; and

- WHEREAS, Grupo A are parties to this Agreement for the purposes, inter alia,
  of terminating the Shareholders' Agreement with effect from the Closing Date.

NOW THEREFORE, in consideration of the mutual covenants set forth herein and
for other good and valuable consideration, the adequacy, receipt and
sufficiency of which are hereby acknowledged, the parties hereby agree as


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follows:


                            SECTION 1 - DEFINITIONS.

SECTION 1.1  DEFINITIONS.  In addition to other terms defined elsewhere herein,
the following terms shall have the meanings assigned to them below (such terms
to be equally applicable to both singular and plural forms of the terms defined
or referred to):

"AFFILIATE" or "affiliate" shall mean, with respect to any specified Person,
any Person directly or indirectly controlling, controlled by, or under common
control with, such specified Person; provided that in the case of a Person who
is an individual, such terms shall also include members of such specified
Person's immediate family.

"ARGENTINA" shall mean the Republic of Argentina.

"BUSINESS DAY" shall mean any day other than a Saturday, Sunday or legal
holiday on which banking institutions in New York City, United States of
America are open for the transaction of normal banking business.

"CLOSING" shall have the meaning ascribed to such term in Section 2.2 hereof.

"CLOSING DATE" shall have the meaning ascribed to such term in Section 2.2
hereof.

"CNV" shall mean the Comision Nacional de Valores of Argentina.

"CONTROL" or "control" when used with respect to any Person, shall mean the
power to direct the management and policies of such person, whether through the
ownership of voting securities, by contract or otherwise; and the terms
"controlling" and "controlled" have meanings correlative to the foregoing.

"U.S.$" and "DOLLARS" shall mean the lawful currency of the United States of
America.

"FCC" shall mean the United States Federal Communications Commission.


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                                        3



"GOVERNMENTAL AUTHORITY" shall mean any nation or government, any state or
other political subdivision thereof, any central bank (or similar monetary or
regulatory authority) thereof, any entity exercising executive, legislative,
judicial, regulatory or administrative functions of or pertaining to
government, and any corporation or other entity owned or controlled, through
stock or capital ownership or otherwise, by any of the foregoing, including,
without limitation, the CNV and the FCC.

"GOVERNMENTAL AUTHORIZATIONS" shall mean any approvals, authorizations,
permits, consents, exemptions and licenses and other actions of or by, and
notices to or filings or registrations with, any Governmental Authority.

"IRS" shall mean the United States Internal Revenue Service or any successor,
agency, and, to the extent relevant, the United States Department of the
Treasury.

"LIEN" shall mean any mortgage, pledge, security interest, encumbrance, lien or
charge of any kind (including, without limitation any conditional sale or other
title retention agreement or lease in the nature thereof, any sale with
recourse against the seller or any Affiliate of the seller, or any agreement to
give any security interest).

"PERSON" shall mean an individual, partnership, corporation, business trust,
joint stock company, trust, unincorporated association, joint venture, or other
entity of whatever nature.

"P$" shall mean the lawful currency of Argentina.

"REPRESENTATIVE" shall mean, with respect to a particular Person, any director,
officer, employee, general partner, limited partner, co-owner, member, nominee,
managing director or controlling Person of such Person.

"SUBSIDIARY" shall mean, with respect to any Person, any Person directly or
indirectly controlled by such Person.  For purposes of this definition,
"control" of a Person means the power, direct or indirect, to vote more than
fifty percent (50%) of the securities having voting power for the election of
directors of such Person or otherwise to direct or cause the direction of the
management and policies of such Person, whether by contract or otherwise.


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<PAGE>   6
    "TRANSFER" or "TRANSFER" shall mean any direct or indirect sale, assignment,
    mortgage, transfer, pledge, gift, hypothecation or other disposition of or
    transfer of capital stock.  The term "Transfer" used as a verb has a
    corresponding meaning.


                  SECTION 2 - TRANSFER OF SHARES AND CLOSING.

    Section 2.1  Transfer of Shares

(a) At the Closing provided for in Section 2.2 STET shall transfer to Nevasa or
    any designated asignee (as specified in Section 9.8 below), free and clear
    of any Liens, the Shares along with all rights and privileges in the respect
    of the Shares (including without limitation, any existing or future rights
    to dividends, distribution, royalties, fees or other amounts payable or
    owning to STET in respect of the Shares or the Shareholders' Agreement) and
    Nevasa or any designated asignee shall purchase the Shares for the Purchase
    Price.

(b) The Purchase Price shall be paid by Nevasa  as follows. At the Closing,
    Nevasa shall deliver to STET U.S.$125.000.000 in inmediately available funds
    by wire transfer to an account designated by STET (the "STET Account") no
    later than the third Business Day prior to the Closing Date at a bank in the
    City of New York, State of New York, United States of America.

    Section 2.2 Closing

    The closing of the transactions contemplated by this Agreement (the
    "Closing") shall take place at 10:00 a.m. on march 16, 1998, or 10 a.m. on
    March 19, 1998, if any of the parties request so by giving writen notice of
    suchto the other parties at least 3 (three) Business Days prior to March 16,
    or such other date 8which shall be a Business Day) as shall be agreed to
    between Nevasa and STET (the "Closing Date") at the offices of Arnold &
    Poter, 399 Park Avenue, New York City, New York, United States of America.
    At the Closing, the following events shall take place:

(a) STET shall deliver to Nevasa a copy of the minutes of a meeting of its board
    of directors authorizing the execution and performance by STET of this
    Agreement (including the termination of the Shareholders' Agreement) and any


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<PAGE>   7


     documents to be entered into at Closing to which it is a party together
     with:

     (i)   a certificate issued by a civil law notary stating that the photocopy
           of such minutes attached to such certificate is a true copy of the
           original; and

     (ii)  a certificate issued by a civil law notary that the person who has
           signed any powers of attorney on behalf of STET is duly authorized to
           represent STET;

(b)  Nevasa shall deliver to STET a copy of the minutes of a duly held meeting
     of its board of directors authorizing the execution and performance by
     Nevasa of this Agreement (including the termination of the Shareholders'
     Agreement) and any documents to be entered into at Closing to which it is a
     party, certified as correct by the secretary of Nevasa together with any
     power of attorney granted thereunder, if any;

(c)  CORIM shall deliver to STET a certified copy of the minutes of a duly held
     meeting of its board of directors authorizing the execution and performance
     by CORIM of this Agreement (including the termination of the Shareholders'
     Agreement) and any documents to be entered into at Closing to which it is a
     party, together with any power of attorney granted thereunder, if any;

(d)  Militello shall deliver to STET a certified copy of the minutes of a duly
     held meeting of its board of directors authorizing the execution and
     performance by Militello of this Agreement (including the termination of
     the Shareholders' Agreement) and any documents to be entered into at
     Closing to which it is a party, together with any power of attorney granted
     thereunder, if any;

(e)  Rotling shall deliver to STET a certified copy of the minutes of a duly
     held meeting of its board of directors authorizing the execution and
     performance by Rotling of this Agreement (including the termination of the
     Shareholders' Agreement) and any documents to be entered into at Closing to
     which it is a party, together with any power of attorney granted
     thereunder, if any;

(f)  The Company shall deliver to STET a certified copy of the minutes of a duly
     held meeting of its board of directors authorizing the execution and
     performance by the Company of this Agreement and any documents to be
     entered into at Closing to which it is a party, certified as correct by the



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<PAGE>   8
     secretary of the Company, together with any power of attorney  granted
     thereunder, if any;

(g)  IMPSAT Argentina shall deliver to STET a certified copy of the minutes of a
     duly held meeting of its board of directors authorizing the execution and
     performance by IMPSAT Argentina of this Agreement and any documents to be
     entered into at Closing to which it is a party, together with any power of
     attorney  granted thereunder, if any;

(h)  Nevasa shall pay the Purchase Price to STET in inmediately available funds
     by wire transfer to the STET Account designated in acordance with Section
     2.1(b) hereof;

(i)  STET, after having received confirmation from its bank that the Purchase
     Price has been irrevocably credited to the STET Account, shall deliver to
     Nevasa or its designated asignee certificates representing the Shares,
     together with any endorsements or stock powers necessary for the
     registration of the transfer of such Shares to Nevasa or its designated
     asignee;

(j)  In respect of the IMSAT Shares, STET shall deliver to IMPSAT Argentina
     written notice of the transfer of such IMPSAT Shares, and, upon receipt
     thereof Nevasa shall procure that a board meeting of IMPSAT Argentina be
     held at which it shall be resolved that:

     (i)   the transfer be registered in the Stock Ledgers of IMPSAT Argentina
           (the "Libro Registro de Acciones");

     (ii)  the resignations of the representatives of STET as directors of
           IMPSAT Argentina (as referred to in Section 2.2 (k) below) be
           tendered and accepted so as to take effect at Closing; and

     (iii) a shareholders' meeting of IMPSAT Argentina be convened and held at
           which it be resolved that :

           (a)  each of the persons nominated by Nevasa shall be appointed
                directors of IMPSAT Argentina, as Nevasa shall direct; and
 


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<PAGE>   9



    (b)   the action taken by each of the representatives of STET resigning as
          directors of IMPSAT Argentina up to the Closing Date shall be
          approved; and

(k) All representatives of STET shall resign effective at the Closing Date from
    their positions as directors of the Company, IMPSAT Argentina or any other
    Subsidiaries of the Company and STET shall deliver to Nevasa such
    resignations letters, reflecting such resignations. The resignation letters
    shall be substantially in the form of Exhibit 2 hereto.


Section 2.3  Termination of Shareholders Agreement.

Effective as of the Closing Date, and subject to the terms and conditions of
this Agreement, each of STET, Nevasa and Grupo A agree that the Shareholders
Agreement shall be terminated in its entirety and be of no further force and
effect. Not withstanding the provision made in Clause 19 (Survival) of the
Share Holders Agreemnet, the parties hereto acknowledge and agree that this
Agreement shall terminate whith regard to Clause 10 (Confidentiality) and
Clause 13 (Applicable Law) of the Shareholders' Agreement.

Section 2.4  Further Actions.

In addition to the matters set forth above in this Section 2, the parties
hereto prior to, at or after the Closing Date shall do and perform or cause to
be done and performed all such further reasonable acts and things and shall
execute and deliver all such other agreements, certificates, instruments and
documents reasonably necessary, proper or advisable to give full legal effect
to the transactions specified in Section 2 and to carry out the intent and
accomplish the purposes of this Agreement and the consummation of the
transactions contemplated hereby.


                        SECTION 3 - CONDITIONS PRECEDENT

Section 3.1  Conditions to Obligations of Nevasa.

The obligations of Nevasa to consummate the transactions contemplated hereby
shall be subject to the satisfaction (or waiver by Nevasa in writing delivered
to



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STET), on or prior to the Closing Date, of each of the following conditions:

(a) the representations and warranties of STET contained herein shall have been
    true and correct in all material respects when made and shall be repeated
    and be true and correct in all material respects as of the Closing Date, and
    STET shall have delivered a certificate from one of its duly authorized
    officers certifying to the foregoing in the form of Exhibit 3 ;

(b) STET shall have performed and complied with in all material respects all
    agreements and conditions contained in this Agreement required to be
    performed or complied with by it prior to or at the Closing Date; and

(c) all Governmental Authorizations and all approvals of, or filings with, any
    other Person required to be obtained or made by STET in connection with the
    execution, delivery and performance by STET of this Agreement shall have
    been obtained or made by STET and shall be in full force and effect.

Section 3.2  Conditions to Obligations of STET.

The obligations of STET to consummate the transactions contemplated by this
Agreement shall be subject to the satisfaction (or waiver by STET in writing
delivered to Nevasa), on or prior to the Closing Date, of each of the following
conditions:

(a) the representations and warranties of Nevasa contained herein shall have
    been true and correct in all material respects when made and shall be
    repeated and be true and correct in all material respects as of the Closing
    Date with respect to Nevasa  and its designated asignee and Nevasa and its
    designated asignee shall have delivered a certificate from one of its duly
    authorized officers certifying to the foregoing in the form of Exhibit 3 for
    Nevasa and in the for of Exhibit 4 for its designated asignee, if any ;

(b) Nevasa  and its designated asignee shall have performed and complied with in
    all material respects all agreements and conditions contained in this
    Agreement required to be performed or complied with by it prior to or at the
    Closing Date;

(c) All Governmental Authorizations and all approvals of, or filings with, any
    other Person required to be obtained or made by Nevasa and its designated



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    asignee in connection with the execution, delivery and performance by Nevasa
    of this Agreement shall have been obtained or made by Nevasa and shall be in
    full force and effect; and

(d) Nevasa shall procure that the Company shall execute a certificate in the
    form of Exhibit 5 to this Agreement and mail the respective notice to the
    IRS giving evidence to STET of such mailing.


Section 3.3  Conditions to Obligations of the Parties.

The obligations of Nevasa and STET to consummate the transactions contemplated
by this Agreement shall be subject to the condition that there shall be no
judgment, order or decree of any court and no order, notice or regulation of
any applicable Governmental Authority in effect and, no material or significant
third party litigation, proceeding, or investigation pending or threatened
before any court or Governmental Authority having jurisdiction over the matter
or any of the parties hereto in each case that would restrain, prohibit or seek
to restrain or prohibit the consummation of the transactions contemplated by
this Agreement in any material respect.

                              SECTION 4 - PAYMENTS

Section 4.1  No Set-Off, Etc.

Except as required by applicable law, all payments to be made pursuant to this
Agreement shall be made in the currency in which such amount is stated to be
due and payable without set-off or counterclaim.  In the event of any
deduction or withholding for or on account of, or any other required payment of
any taxes, levies, imposts, duties, fees, assessments, restrictions, conditions
or other charges of whatever nature (including any registration, stamp,
documentary or similar taxes, fees or charges) (collectively "Taxes"), are due
and payable in respect of the payment of the Purchase Price and the transfer of
the Shares, STET shall be responsible for the payment of all such Taxes and all
interest, penalties or similar liabilities with respect thereto required by law
to be paid by the seller of the Shares and Nevasa shall be responsible for the
payment of all such Taxes and all interest, penalties or similar liabilities
with respect thereto, required by law to be paid by the buyer of the Shares.



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                   SECTION 5 - REPRESENTATIONS AND WARRANTIES

Section 5.1  Representations and Warranties of STET.

STET hereby represents and warrants to Nevasa as follows:

(a) STET is a corporation duly organized, validly existing under the laws of The
    Netherlands, with full power and authority to execute, deliver and perform
    its obligations under this Agreement, including all documents executed or to
    be executed in connection herewith or therewith;

(b) This Agreement and all documents executed or to be executed in connection
    herewith have been, or as of the date of such execution will be, duly and
    validly authorized, executed and delivered by STET;

(c) Neither the execution, delivery and performance of this Agreement and all
    documents executed or to be executed in connection herewith by STET
    violates, has resulted or will result in a breach of any of, or constitutes
    a default (or an event which with or without notice and/or lapse of time
    would constitute a default) under, STET's organizational documents or
    by-laws, or any agreement or instrument to which STET is a party or by which
    STET or its assets or revenues are bound, or any statute, order, rule or
    regulation of any court or other Governmental Authority applicable to STET;

(d) This Agreement and all documents executed or to be executed in connection
    herewith are the legal, valid and binding obligations of STET, enforceable
    against STET in accordance with their respective terms, except as such
    enforceability may be limited by applicable bankruptcy, insolvency,
    reorganization and similar laws affecting creditors' rights generally,
    moratorium laws from time to time in effect, and by equitable principles
    restricting the availability of equitable remedies; and

(e) The Shares are owned beneficially and legally by STET and will be
    transferred to Nevasa or its designated asignee on the Closing Date free and
    clear of any Liens.

Section 5.2  Representations and Warranties of Nevasa.



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Nevasa hereby represents and warrants to STET as follows:

(a) Nevasa is a corporation duly organized and, validly existing under the laws
    of the Republic of Ireland, with full power and authority to execute,
    deliver and perform its obligations under this Agreement, including all
    documents executed or to be executed in connection herewith and therewith;

(b) This Agreement and all documents executed or to be executed in connection
    herewith and therewith have been, or as of the date of such execution will
    be, duly and validly authorized, executed and delivered by Nevasa;

(c) Neither the execution, delivery and performance of this Agreement and all
    documents executed or to be executed in connection herewith by Nevasa
    violates, has resulted or will result in a breach of any of, or constitutes
    a default (or an event which with or without notice and/or lapse of time
    would constitute a default) under, Nevasa's Memorandum of Incorporation and
    Articles of Association, or any agreement or instrument to which Nevasa is a
    party or by which Nevasa or its assets or revenues are bound, or any
    statute, order, rule or regulation of any court or other Governmental
    Authority applicable to Nevasa; and

(d) This Agreement and all documents executed or to be executed in connection
    herewith are the legal, valid and binding obligations of Nevasa, enforceable
    against Nevasa in accordance with their respective terms, except as such
    enforceability may be limited by applicable bankruptcy, insolvency,
    reorganization and similar laws affecting creditors' rights generally,
    moratorium laws from time to time in effect, and by equitable principles
    restricting the availability of equitable remedies.

                             SECTION 6 - COVENANTS

Section 6.1  Confidentiality of Information.

For a period of three years from the Closing Date, STET shall not, and shall
ensure that its directors, officers and employees shall not, use, disclose or
otherwise make public for any and all purposes, any information, facts or
discoveries (including, without limitation any business, financial and
technical


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<PAGE>   14


information and data) (collectively "Information"), developed, gained or
obtained as a result of, or in the performance of, the Shareholders Agreement
or by virtue of STET's ownership interest in or representation on the Board of
Directors of the Company, IMPSAT Argentina and any other Subsidiary of the
Company (including for this purpose IMPSAT Comunicacoes Ltda. ("IMPSAT do
Brasil"), and STET shall ensure that all such Information shall be held
strictly confidential by STET and all of its directors, officers and employees.
The foregoing restrictions shall not apply to any Information that:  (a) has
become or becomes publicly available other than as a result of any action or
omission by STET or any of its directors, officers or employees in violation of
this Agreement; (b) has been known or developed independently by STET or its
Affiliates or Representatives prior to the receipt of any such Information from
the Company, IMPSAT Argentina or any such other Subsidiary of the Company; or
(c) is required by law to be disclosed to any Governmental Authority or STET is
obliged to produce under order of a court of competent jurisdiction; provided,
however, that prior to making any such disclosure to any Governmental Authority
STET shall provide Nevasa with prior written notice and, where reasonably
practicable, provide Nevasa an opportunity so that Nevasa, the Company or
IMPSAT Argentina may seek (with STET's cooperation, if so requested by Nevasa)
a protective order or other appropriate remedy.

Section 6.2  Solicitation of Employees.

For a period of two years from the Closing Date, STET shall not and shall use
its reasonable efforts to ensure that its Affiliates and Representatives shall
not initiate or mantain contact with any present or former employee of the
Company or any of its Subsidiaries (including for this purpose IMPSAT do
Brasil) regarding any non-public information relating to the business,
prospects, operations or finances of the Company and its Subsidiaries, or hire
or seek to hire any such present or former employee (the latter having left the
Company or any of its Affiliates within the last two years of such hiring) in
any capacity, or induce or seek to induce any present employee to leave such
employment

Section 6.3  No Disparagement.

Nevasa and STET shall not, and shall use their reasonable efforts to ensure
that each of their respective Affiliates and Representatives shall not, make or
publish any disparaging statements, whether verbal or written, regarding any
other party



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<PAGE>   15

hereto (or such other party's Affiliates, directors, officers, employees,
exclusive agents, products, services or business capabilities) which materially
adversely affects the goodwill or business of such other party ; however, any
truthful statement made, given or communicated to any Governmental Authority
shall not be deemed to be diparaging.

Section 6.4  Equitable Remedies.

STET acknowledges that the payment of the Purchase Price includes consideration
for the obligations of STET contained in Sections 6.1, 6.2  hereof, and the
parties agree that Sections 6.1, 6.2 hereof  may be enforced by a mandatory
injunction or other form of equitable relief appropriate and applicable to
ensure its specific performance, but these rights shall not be construed as a
limitation of any other available remedies.

                    SECTION 7 - RELEASES AND INDEMNIFICATION

Section 7.1  Releases and Indemnities of the Nevasa Released Parties.

(a) Effective as of the Closing Date, STET and each of its Affiliates and
    Representatives (the "STET Releasing Parties") shall hereby voluntarily,
    knowingly, finally and irrevocably release, relinquish, waive and forever
    discharge Nevasa, each Person in Grupo A., the Company, IMPSAT Argentina,
    all other Subsidiaries of the Company and their respective Affiliates and
    Representatives (the "Nevasa Released Parties") from any and all legal,
    equitable or other claims, actions, proceedings, causes of action, suits,
    debts, contracts, controversies, agreements, promises, damages, judgments,
    executions, demands and liabilities of any nature whatsoever, whether known
    or unknown, suspected or unsuspected, fixed or contingent  (collectively,
    "Claims"), that any of the STET Releasing Parties possesses or could possess
    or has asserted or could have asserted against any of the Nevasa Released
    Parties with respect to, in connection with, or in any way related to or
    arising out of the Shareholders Agreement, any actions or omissions by any
    of the Nevasa Released Parties with respect to the Company or IMPSAT
    Argentina  (including actions and omissions by any Affiliates of the Nevasa
    Released Parties in any capacity as Representatives or agents of the
    Company, IMPSAT Argentina or any other Subsidiary of the Company), and each
    of the STET Releasing Parties agrees not to assert against any of the Nevasa
    Released



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<PAGE>   16


    Parties any such Claims, excepting only any Claims arising by virtue of any
    violation or threatened violation of this Agreement.

    The parties acknowledge and agree that the releases described in the
    foregoing sentence shall not apply in respect of the of U.S.$810,000 and
    U.S.$60,000 due and payable under invoices dated February 11, 1998 and
    numbered 3/71 and 4/71, by Resis Ingenieria S.A. to STET International
    S.p.A. and /or STET with respect to certain Stet Representatives seconded to
    the Company.

(b) Each of the Nevasa Released Parties hereby agrees to indemnify and hold
    harmless each of the STET Released Parties (as defined below) and their
    respective directors, officers, agents, and employees (each, a "STET
    Indemnitee") from any losses, liability, loss, cost, expense (including all
    reasonable attorneys' fees), penalties, assessments or fines (including all
    actions or claims in respect thereof (collectively, "Losses") that may be
    imposed on, incurred by or asserted against any STET Indemnitee arising out
    or resulting from or by reason of any breach by Nevasa of any
    representation, warranty, covenant or other provision contained in this
    Agreement or any document to be delivered pursuant to this Agreement.

    For the avoidance of doubt and notwithstanding the foregoing, each of the
Company Releasing Parties (as defined below) hereby accepts to indemnify and
hold harmless each of STET's Representatives who served as directors or officers
of the Company or any of its Affiliates to the extent that such directors or
officers were indemnified under Section 10 of Article 3 of the By-laws of the
Company

Section 7.2  Releases and Indemnities of STET.

(a) Effective as of the Closing Date, each of Nevasa, each Person in Grupo A,
    the Company, IMPSAT Argentina and their respective Affiliates and
    Representatives (the "Company Releasing Parties") shall hereby voluntarily,
    knowingly, finally and irrevocably release, relinquish, waive and forever
    discharge STET and its Affiliates and Representatives (the "STET Released
    Parties") from any and all Claims that any of the Company Releasing Parties
    possesses or could possess or has asserted or could have asserted against
    any of the STET Released Parties with respect to, in connection with, or in
    any way related to or arising out of, the Shareholders Agreement, any
    actions or omissions by any of the STET Released



                                        15
<PAGE>   17


    Parties with respect to the Company, or any of its Affiliates (including
    actions and omissions by any of the STET Released Parties in any capacities
    as Representatives or agents of the Company, IMPSAT Argentina or any other
    Subsidiary of the Company), and each of the Company Releasing Parties agrees
    not to assert against any of the STET Released Parties any such Claim,
    excepting only any Claim arising by virtue of any violation or threatened
    violation of this Agreement.

(b) STET hereby agrees to indemnity and hold harmless each of the Nevasa
    Released Parties and their respective directors, officers, agents, and
    employees  (each, a "Nevasa Indemnitee") from any Losses that may be imposed
    on, incurred by or asserted against any Nevasa Indemnitee arising out or
    resulting from or by reason of any breach by STET of any representation,
    warranty, covenant or other agreement contained in this Agreement.

Section 7.3 Scope of Releases

The releases provided for in section 7.1 and 7.2 hereof shall not apply in
respect of any liability of a Nevasa Released Party or a STET Released Party
that arises out of or relates to any written agreement, contract, obligation,
promise, or undertaking between a Company Releasing Parties and a STET
Releasing Party for the purchase and sale of goods or services or any other
such commercial undertaking.

                            SECTION 8 - TERMINATION

Section 8.1  Grounds for Termination.  This Agreement may be terminated at any
time on or before the Closing Date by;

(a) The written agreement of Nevasa and STET;

(b) Nevasa, upon ten (10) Business Days' prior written notice, upon the breach
    by STET of any of its representations, warranties, covenants or agreements
    contained in this Agreement or in the event that STET should fail to cause
    to occur any condition that is a condition precedent to the obligations of
    Nevasa hereunder or if satisfaction of such a condition is or becomes
    unlikely to be attainable by STET before the Closing Date (other than
    through the failure of Nevasa to comply with its obligations under this
    Agreement) and Nevasa has


                                        16
<PAGE>   18


    not waived such condition or breach on or before the Closing Date; provided,
    however, that STET shall have a period of ten (10) Business Days to cure or
    correct any such breach or to cause to occur any such condition;

(c) STET, upon ten (10) Business Days' prior written notice, upon the breach by
    Nevasa of any of its representations, warranties, covenants or agreements
    contained in this Agreement or in the event that Nevasa should fail to cause
    to occur any condition that is a condition precedent to the obligations of
    Nevasa hereunder; or if satisfaction of such a condition is or becomes
    unlikely to be attainable by Nevasa before the Closing Date (other than
    through the failure of STET to comply with its obligations under this
    Agreement) and STET has not waived such condition or breach on or before the
    Closing Date; provided, however, that Nevasa shall have a period of ten (10)
    Business Days to cure or correct any such breach or to cause to occur any
    such condition.


                           SECTION 9 - MISCELLANEOUS

Section 9.1  Amendments; Waivers.

(a) No amendment of any provision of this Agreement shall be effective unless it
    is in writing and signed by Nevasa and STET, and no waiver of any provision
    of this Agreement, nor consent to any departure by any party hereto, shall
    be effective unless it is in writing and signed by Nevasa and STET, and then
    such waiver or consent shall be effective only in the specific instance and
    for the specific purpose for which it is given.

(b) No failure on the part of any party to exercise, and no delay in exercising,
    any right, power or privilege hereunder or under any document referred to in
    this Agreement shall operate as a waiver thereof by such party, nor shall
    any single or partial exercise of any such right, power or privilege
    preclude any other or further exercise thereof or the exercise of any other
    right, power or privilege. The rights and remedies of each party provided
    herein and in the documents referred to in this Agreement (i) are cumulative
    and are in addition to, and not exclusive of, any rights or remedies
    provided by law, and (ii) are not conditional or contingent on any attempt
    by such party to exercise any of its rights under any of the documents
    referred to in this Agreement against the other party or any other entity.



                                        17
<PAGE>   19



Section 9.2  Notices.

Except as expressly set forth herein, all demands, notices, requests, consents,
and communications hereunder shall be in writing and shall be deemed to have
been duly given if personally delivered by courier service or messenger, or
sent by overnight delivery service or facsimile transmission, to the following
addresses, or such other addresses as may be furnished hereafter by notice in
writing, to the following parties:

(i)   in the case of Nevasa:
NEVASA HOLDINGS LTD.
Address: Av. E. Madero 940-19th Floor
     Buenos Aires - Argentina
Attention: Mr. Enrique Pescarmona
Telecopy No.: + 54 1 316 8868;

(ii)  in the case of Grupo A
GRUPO A
Address: Av. E. Madero 940-19th Floor
     Buenos Aires - Argentina
Attention: Mr. Enrique Pescarmona
Telecopy No.: + 54 1 316 8868;

(iii) in the case of STET:
STET INTERNATIONAL NETHERLANDS NV
Address: Strawiskylaan 6th Floor
     'Atrium' 3111
     ZX 1077 Amsterdam - the Netherlands
Attention: Chief Executive Officer
Telecopy No.:+ 31 20 3011101.

(iv)  in case of the Company
IMPSAT CORPORATION
Address: Alferez Pareja 256
     Buenos Aires - Argentina
Attention: Chief Executive Officer
Telecopy No: +54 1 362 5030


                                        18
<PAGE>   20



(v) in case of IMPSAT Argentina
IMPSAT Argentina S.A.
Address: Alferez Pareja 256
     Buenos Aires - Argentina
Attention: Chief Executive Officer
Telecopy No: +54 1 362 5030

All demands, requests, consents, notices and communication shall be deemed to
have been received if addressed in the manner described above, (i) at the time
of actual delivery thereof by hand, by courier service or by facsimile
transmission, or (ii) if sent by overnight delivery service, three (3) Business
Days after deposit thereof with such delivery service.

Section 9.3  Governing Law.

This Agreement shall  be construed and the obligations of the parties
thereunder shall be determined in accordance with the Laws of the State of New
York, United States of America.

Section 9.4 Arbitration.

(a) In the event that any dispute, disagreement, controversy, question or claim
    arises out of or in connection with this Agreement, including without
    limitation any question relating to its existence, validity, application,
    interpretation, performance, breach, termination and /or enforcement (a
    "Dispute"), any party may give written notice to the other parties requiring
    them to seek to reach an amicable settlement of the Dispute. If no amicable
    settlement is reached within 3 business Days of such notice, the Dispute
    shall be referred to and finally resolved by Arbitration under the
    International Arbitration Rules of the American Arbitration Association (the
    "Rules"), which Rules are deemed to be incorporated by reference into this
    Section.

(b) The tribunal (the "Tribunal") shall consist of three arbitrators (the
    "Arbitrators", and each an "Arbitrator"). If there are only two parties to
    the Dispute, the claimant (the "Claimant") shall designate an Arbitrator in
    the notice of arbitration which shall be sent to the respondent (the
    "Respondent") and the Respondent shall designate an Arbitrator within 15
    days of receipt of



                                        19
<PAGE>   21
    such notice of arbitration. The party designated Arbitrators shall designate
    the third Arbitrator, who shall be the chairman of the Tribunal within 30
    days of the Respondent's designation of its party Arbitrator. If a party or
    the party - designated Arbitrators should fail to make a designation(s)
    within the time limits set out above, the administrator shall make the
    appropriate designation(s) on their behalf. If there is more than one
    Claimant party and /or more than one Respondent party, the Claimant paries
    shall together designate one Arbitrator in the notice of arbitration and the
    Respondent parties shall together designate one Arbitrator within 15 days of
    the receipt by the last of them , of the designation of the Claimant's party
    Arbitrator. If the Claimant parties or the Respondent parties fail to make a
    designation within the time limits set out above, the administrator shall
    designate all three Arbitrators. However, if only the party - designated
    Arbitrators fail to make a designation within the required time, the
    parties' designations shall stand and the administration shall only
    designate the chairman.

(c) If any Dispute raises issues which are substantially the same as or
    connected with issues raised in a Dispute which has already been referred to
    arbitration (an "Existing Dispute"), or arises out of substantially the same
    facts as are subject of an Existing Dispute (a "Related Dispute"), the
    Arbitrators appointed or to be appointed in respect of any such Existing
    Dispute shall also be appointed as the Arbitrators in respect of any Related
    Dispute.

(d) The Tribunal upon the request of one of the parties to a Dispute or a party
    to this Agreement which itself wishes to be joined in any arbitration
    proceedings in relation to a Dispute may join any party to this Agreement to
    any arbitration proceedings in relation to such Dispute and may make a
    single, final award determining the Dispute between them. Each of the
    parties to this Agreement hereby consents to be joined to any arbitration
    proceedings in relation to any Dispute at the request of a party to such
    Dispute.

(e) Where pursuant to the above provisions, the same Arbitrators have been
    appointed in relation to two or more Disputes, the Arbitrators may, with the
    agreement of all the parties concerned or upon the application of one of the
    parties, being a party to each of the Disputes order that the whole or part
    of the matters at issue shall be heard together upon such terms  or
    conditions as the Arbitrators see fit. The Arbitrators shall have power to
    make such directions and any provisional, interim or partial award as they
    consider just and



                                        20
<PAGE>   22


    desirable.

(f) The parties agree that any Arbitrators chosen pursuant to this Section 9.4
    will not in any manner be related to or affiliated with any of the parties
    involved in such arbitration.

(g) Except as otherwise set out in this Section, the arbitration proceedings
    shall be conducted in accordance with, and shall be subject to the Rules.
    The location of any arbitration proceedings will be New York, United States
    of America and any arbitration proceedings shall be conducted in English and
    all arbitration awards hereunder shall be rendered and paid in Dollars.

(h) The determination of the Arbitrators shall be conclusive and binding upon
    the parties to such arbitration proceedings.

(i) The expenses of each party, including legal and accounting fees, if any,
    with respect to any arbitration proceeding shall be borne by such party,
    except to the extent otherwise directed by the Arbitrators, who shall
    endeavour to allocate them among the disputing parties based upon the
    relative merits of their cases. The Arbitrators shall designate the party to
    bear the expenses of the Arbitrators or the respective amounts of such
    expenses to be borne by each party.


Section 9.5  Confidentiality.

Each party agrees that, without the prior written consent of the other parties
hereto, it shall not disclose the terms of this Agreement to any person or
entity, except (i) as may be required by law or regulation, or by an order,
judgment or decree of a court or other governmental authority of competent
jurisdiction, (ii) to such party's Affiliates, employees, partners, agents,
attorneys, representatives, officers, trustees, directors, accountants and
investment advisors who have legitimate business reason for such information
and are informed in writing of the confidential nature of such information or
(iii) as may be required to be disclosed to governmental, regulatory or other
official institutions, or to investment or commercial banks or other financial
institutions (and their advisors and representatives) in connection with any
contemplate financing transaction.

Section 9.6  Costs and Expenses.




                                        21
<PAGE>   23



Except as otherwise specifically provided in this Agreement each party to this
Agreement shall bear its own costs and expenses (including but not limited to
attorneys' fees and expenses) in connection with the preparation, negotiation,
execution and performance of this Agreement and the transactions contemplated
hereby.

In the event this Agreement is terminated by either of Nevasa or STET pursuant
to Section 8.1(b) or (c), as applicable, STET or Nevasa as the case may be,
shall reimburse the terminating party in respect of the costs and expenses
(including but not limited to attorneys' fees and expenses) incurred by such
terminating party up to the date of termination in connection with the
preparation, negotiation, execution and performance of this Agreement and the
transactions contemplated hereby.

Section 9.7  Counterpart Execution; Entire Agreement.

This Agreement may be executed in any number of counterparts, each of which,
when so executed and delivered, shall be deemed an original, and all of which
together shall constitute one agreement binding all of the parties hereto.

This Agreement (together with the documents refered to herein) contains the
entire understanding of the parties with respect to its subject matter.  This
Agreement supersedes all prior negotiations, representations, agreements and
understandings, whether oral or written, between the parties hereto with
respect to its subject matter.

Section 9.8 Assignment.

Neither party may assign any of its rights under this Agreement without the
prior written consent of the other parties, except that Nevasa may assign any
of its rights under this Agreement, including its right to purchase Shares, to
any wholly owned joint stock company of Nevasa. In such case Nevasa shall
notify STET in writing of the permited assignement at least 7 (seven) days
before the Closing Date. Subject to the foregoing, this Agreement will apply
to, be binding in all respects upon, and injure to the benefit of the
successors and permited assigns of the parties. Nothing expressed or referred
to in this Agreement will be construed to give any Person other than the
parties to this Agreement any legal or equitable



                                        22
<PAGE>   24


right, remedy, or claim under or with respect to this Agreement or any
provision of this Agreement. This Agreement and all of its provisions and
conditions are for the sole and exclusive benefit of the parties to this
Agreement and their succesors and assigns. Obligations under this Agreement
shall not be assignable and, for the avoidance of doubt, no assignmet of this
Agreement or any of the rights thereunder shall release the assignor from its
obligation under this Agreement.

Section 9.9 Severability.

If any provision of this Agreement is held invalid or unforceable by any court
or other body of competent jurisdiction, the other provisions of this Agreement
will remain in full force and effect. Any provision of this Agreement held
invalid or unforceable only in part or degree will remain in full force and
effect to the extent not held invalid or unforceable.


IN WITNESS WHEREOF, this Agreement has been duly executed and delivered by the
duly authorized officers of each of the parties on the day and year first above
written.


<TABLE>
        <S>                           <C>
        NEVASA Holdings Ltd.          STET International Netherlands NV


        By:_________________________  By: _________________________
        Name:ENRIQUE M. PESCARMONA    Name: MASSIMO MASINI
        Title: PRESIDENT              Title: CEO

        CORPORACION IMPSA, S.A.       MILITELLO LIMITED


        By:_________________________  By:_________________________
        Name:ENRIQUE M. PESCARMONA    Name:ROBERTO A. VIVO CHANETON
        Title: PRESIDENT              Title: DIRECTOR

        ROTLING INTERNATIONAL         ROBERTO A. VIVO CHANETON
        CORPORATION

        By: ________________________  By:___________________________
</TABLE>

                                        23
<PAGE>   25


        Name: RICARDO A. VEDAGUER
        Title: PRESIDENT

        Ricardo A. Verdaguer          IMPSAT CORPORATION


        By:_________________________  By:_________________________
                                      Name:RICARDO A. VERDAGUER 
                                      Title: PRESIDENT
       
       IMPSAT S.A.
       
       By:_________________________
       Name: RICARDO A. VERDAGUER
       Title: PRESIDENT


                                       24