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                                                                    EXHIBIT 10.1

                                AMENDMENT NO. 1


          AMENDMENT NO. 1, dated as of April 21, 2000 (this "Amendment"), to the
                                                             ---------
Credit Agreement, dated as of August 17, 1999 (the "Credit Agreement"), among
                                                    ----------------
INFONET SERVICES CORPORATION, a Delaware corporation (the "Borrower"), the
                                                           --------
several banks and other financial institutions or entities from time to time
parties thereto (the "Lenders"), MERRILL LYNCH & CO., as lead arranger, book
                      -------
manager and syndication agent (in such capacity, the "Arranger"), THE BANK OF
                                                      --------
NOVA SCOTIA, as administrative agent (in such capacity, the "Administrative
                                                             --------------
Agent"), and SOCIETE GENERALE, as documentation agent (in such capacity the
-----
"Documentation Agent").
--------------------

                                 W I T N E S S E T H:
                                 - - - - - - - - - -

          WHEREAS, the Borrower has requested the Lenders to consent to amend
the  Credit Agreement to change the limitations on (a) Capital Expenditures and
(b) Investments;

          WHEREAS, the Administrative Agent and the Lenders are willing to
consent to the requested amendments on and subject to the terms and conditions
contained herein;

          NOW THEREFORE, in consideration of the premises and mutual covenants
hereinafter set forth, the parties agree as follows:

     I.   Definitions.  Unless otherwise defined herein, terms defined in the
          -----------
Credit Agreement are used herein as therein defined.

     II.  Amendments to Credit Agreement.
          ------------------------------

          2.1   Section 7.7.  Section 7.7 of  the Credit Agreement is hereby
                -----------
amended by deleting such section in its entirety and substituting in lieu
thereof the following new Section 7.7:

          "7.7 Limitation on Capital Expenditures.  Make or commit to make any
               ----------------------------------
          Capital Expenditure, except:

               (a)  Capital Expenditures of the Borrower and its Subsidiaries in
          the ordinary course of business not exceeding $400,000,000 for any
          fiscal year beginning on January 1, 2000; provided that (i) up to 100%
                                                    --------
          of such amount, if not so expended in the fiscal year for which it is
          permitted, may be carried over for expenditure in the next fiscal year
          and (ii) Capital Expenditures made pursuant to this clause (a) during
          any fiscal year shall be deemed made, first, in respect of amounts
                                                -----
          permitted for such fiscal year as
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                                                                               2


          provided above, and second, in respect of amounts carried over from
                              ------
          the prior fiscal year pursuant to subclause (i) above and

               (b) Capital Expenditures made with the proceeds of any
Reinvestment  Deferred Amount."

          2.2   Section 7.8.  Subsection 7.8(h) of the Credit Agreement is
                -----------
hereby amended by deleting "$5,000,000" in line two and substituting in lieu
thereof "$20,000,000."

          2.3   Section 7.17.  Section 7.17 of the Credit Agreement is hereby
                ------------
amended by inserting at the end of such Section the following text:

          "; provided that, with respect to NTC only, such amount shall be
             --------
          $20,000,000."

     III.  Conditions Precedent.  This Amendment shall become effective as of
           --------------------
the date hereof  when each of the conditions precedent set forth below shall
have been fulfilled (the date such conditions are fulfilled, the "Amendment
                                                                  ---------
Effective Date"):
--------------

          3.1    Amendment.  The Administrative Agent shall have received this
                 ---------
Amendment, executed and delivered by a duly authorized officer of each of the
Loan Parties and the Required Lenders.

          3.2    No Default or Event of Default.  On and as of this Amendment
                 ------------------------------
Effective Date and after giving effect to this Amendment and the transactions
contemplated hereby, no Default or Event of Default shall have occurred and be
continuing.

          3.3    Representations and Warranties.  The representations and
                 ------------------------------
warranties made by each Loan Party in each Loan Document to which it is a party
and herein after giving effect to this Amendment and the transactions
contemplated hereby shall be true and correct in all material respects on and as
of this Amendment Effective Date, before and after giving effect to this
Amendment, as if made on such date, except where such representations and
warranties relate to an earlier date in which case such representations and
warranties shall be true and correct as of such earlier date.

     IV.  General.
          -------

          4.1   Representation and Warranties.  The Borrower represents and
                -----------------------------
warrants to each Lender and the Administrative Agent as follows:

          (a)  Corporate Power; Authorization; Enforceable Obligations.
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                                                                               3

               (i)    Each Loan Party has the corporate power and authority, and
          the legal right, to make and deliver this Amendment and to perform the
          Loan Documents to which it is a party, as amended by this Amendment,
          and has taken all necessary corporate action to authorize the
          execution, delivery and performance of this Amendment and the
          performance of such Loan Documents, as so amended.

               (ii)   No consent or authorization of, approval by, notice to,
          filing with or other act by or in respect of, any governmental
          authority or any other Person is required in connection with the
          execution and delivery of this Amendment to which any Loan Party is a
          party or with the performance, validity or enforceability of the Loan
          Documents to which it is a party, as amended by this Amendment.

               (iii)  This Amendment has been duly executed and delivered on
          behalf of each of the Loan Parties party hereto.

               (iv)  This Amendment and each Loan Document to which a Loan Party
          is a party, as amended by this Amendment, constitutes a legal, valid
          and binding obligation of such Loan Party enforceable against such
          Loan Party in accordance with its terms, except as affected by
          bankruptcy, insolvency, fraudulent conveyance, reorganization,
          moratorium and other similar laws relating to or affecting the
          enforcement of creditors= rights generally, general equitable
          principles (whether considered in a proceeding in equity or at law)
          and an implied covenant of good faith and fair dealing.

          (b)  No Legal Bar.  The execution, delivery and performance of this
               ------------
     Amendment and the performance of the Loan Documents to which each Loan
     Party is a party, as amended by this Amendment, will not violate any
     Requirement of Law or contractual obligation of any Loan Party or of any of
     their Subsidiaries and will not result in, or require, the creation or
     imposition of any Lien on any of its or their respective properties or
     revenues pursuant to any such Requirement of Law or contractual obligation.

          (c)  Representations and Warranties in Loan Documents.  The
               ------------------------------------------------
     representations and warranties set forth in each Loan Document are true and
     correct in all material respects as if made on and as of this Amendment
     Effective Date, except as they may specifically relate to an earlier date.

          4.2  Continuing Effect of Credit Agreement.  This Amendment shall not
               -------------------------------------
constitute an amendment of any provision of the Credit Agreement not expressly
referred to herein and shall not be construed as an amendment, waiver or consent
to any action on the part of any party hereto that would require an amendment,
waiver or consent of the Administrative Agent or the Lenders except as expressly
stated herein.  Except as expressly waived hereby, the provisions of the Credit
Agreement are and shall remain in full force and effect.
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          4.3   Affirmation of Security Documents.  Each of the Parties hereto
                ---------------------------------
agrees that the execution and delivery of this Amendment and the performance of
the Credit Agreement shall not in any way affect such Person's obligations under
any Security Document to which such Person is a party, which obligations on the
date hereof remain absolute and unconditional and are not subject to any
defense, set-off or counterclaim.

          4.4   Expenses.  The Borrower agrees to pay or reimburse the
                --------
Administrative Agent for all of its reasonable out-of-pocket costs and expenses
incurred in connection with (a) the negotiation, preparation, execution and
delivery of this Amendment and any other documents prepared in connection
herewith, and consummation of the transactions contemplated hereby and thereby,
including the fees and expenses of Simpson Thacher & Bartlett, counsel to the
Administrative Agent, and (b) the enforcement or preservation of any rights
under this Amendment and any other such documents.

          4.5   GOVERNING LAW.  THIS AMENDMENT SHALL BE GOVERNED BY, AND
                -------------
CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.

          4.6   Counterparts.  This Amendment may be executed in any number of
                ------------
counterparts by the parties hereto, each of which counterparts when so executed
shall be an original, but all counterparts taken together shall constitute one
and the same instrument.

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

                              INFONET SERVICES CORPORATION

                              By:__________________________
                              Name:
                              Title:


                              IINS, INC.

                              By:__________________________
                              Name:
                              Title:
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                              ESG COMMUNICATIONS INCORPORATED

                              By:__________________________
                              Name:
                              Title:


                              INFONET BROADBAND SERVICES CORPORATION

                              By:__________________________
                              Name:
                              Title:


                              MERRILL LYNCH & CO., as Lead Arranger,
                              Book Manager and Syndication Agent

                              By:__________________________
                              Name:
                              Title:


                              MERRILL LYNCH CAPITAL CORPORATION,
                              as Lender

                              By:__________________________
                              Name:
                              Title:
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                              THE BANK OF NOVA SCOTIA, as a Lender and as
                              Administrative Agent

                              By:__________________________
                              Name:
                              Title:
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                              SOCIETE GENERALE, as a Lender and as
                              Documentation Agent

                              By:__________________________
                              Name:
                              Title:
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                              ABN AMRO BANK N.V.

                              By:__________________________
                              Name:
                              Title:


                              By:__________________________
                              Name:
                              Title:
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                              BANQUE PARIBAS

                              By:__________________________
                              Name:
                              Title:


                              By:__________________________
                              Name:
                              Title:
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                              BAYERISCHE HYPO-UND VEREINSBANK AG,
                              New York Branch

                              By:__________________________
                              Name:
                              Title:

                              By:__________________________
                              Name:
                              Title:
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                              FLEET BANK, N.A.

                              By:__________________________
                              Name:
                              Title:
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                              GOLDMAN SACHS CREDIT PARTNERS L.P.

                              By:__________________________
                              Name:
                              Title:
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                              GALAXY CLO 1999-1, LTD.

                              By:   SAI INVESTMENT ADVISER, Inc.,
                                    as its Collateral Manager

                              By:__________________________
                              Name:
                              Title:

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                              THE FUJI BANK, Ltd.

                              By:__________________________
                              Name:
                              Title:

<PAGE>

                              UBS AG,  Stamford Branch

                              By:__________________________
                              Name:
                              Title:


                              By:__________________________
                              Name:
                              Title:

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                              PILGRIM CLO 1999 -- 1 LTD.

                              By:  PILGRIM INVESTMENTS, INC.,
                              as Its Investment Manager


                              By:__________________________
                              Name:
                              Title:

<PAGE>

                              SEQUILS--PILGRIM I LTD.,

                              By: PILGRIM INVESTMENTS, INC.,
                              as Its Investment Manager


                              By:__________________________
                              Name:
                              Title:

<PAGE>

                              ML CLO XX PILGRIM AMERICA
                              (CAYMAN), LTD.

                              By:  PILGRIM INVESTMENTS, INC.,
                              as Its Investment Manager

                              By:__________________________
                              Name:
                              Title:


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                              MORGAN STANLEY DEAN WITTER PRIME
                              INCOME TRUST

                              By:__________________________
                              Name:
                              Title:

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                              KZH SOLEIL-2 LLC

                              By:__________________________
                              Name:
                              Title:


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                              DE NATIONALE INVESTERINGS BANK NV

                              By:__________________________
                              Name:
                              Title:


                              By:__________________________
                              Name:
                              Title:

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                              CITICORP USA, INC.

                              By:__________________________
                              Name:
                              Title:

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                              ARCHIMEDES FUNDING, L.L.C.

                              By:  ING Capital Advisors LLC
                              as Collateral Manager

                              By:__________________________
                              Name:
                              Title:

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                              ING HIGH INCOME PRINCIPAL
                              PRESERVATION FUND HOLDINGS, LDC.,

                              By:  ING Capital Advisors LLC
                              As Investment Advisor

                              By:__________________________
                              Name:
                              Title:

<PAGE>

                              SEQUILS-ING(HBDGM), LTD.

                              By:  ING Capital Advisors LLC,
                              Collateral Manager and
                              Authorized Signatory

                              By:__________________________
                              Name:
                              Title:

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                              LEHMAN COMMERCIAL PAPER, INC.

                              By:__________________________
                              Name:
                              Title:

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                              CREDIT LOCALE DE FRANCE,
                              NEW YORK AGENCY

                              By:__________________________
                              Name:
                              Title:


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                              CREDIT LOCALE DE FRANCE,
                              NEW YORK AGENCY

                              By:__________________________
                              Name:
                              Title: