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                                                                     EXHIBIT 4.9

                             SUPPLEMENTAL INDENTURE

     SUPPLEMENTAL INDENTURE, dated as of January 8, 1999, between FirstCom
Corporation, a Texas corporation (the "Company") (formerly, InterAmericas
Communications Corporation), and State Street Bank and Trust Company, as trustee
under the indenture referred to below (the "Trustee").

                                    RECITALS

     WHEREAS, the Company has heretofore executed and delivered to the Trustee
an indenture, dated as of October 27, 1997 (the "Indenture"), providing for the
issuance of an aggregate principal amount of $150,000,000 of 14% Senior Notes
due 2007 (the "Notes");

     WHEREAS, Sections 2.09 and 9.02 of the Indenture provide that, except with
respect to certain specified provisions of the Indenture, the Indenture may be
amended or supplemented with the consent of the Holders of a majority in
principal amount of the Notes then outstanding voting as a single class, other
than Notes owned by the Company, or by any Person directly or indirectly
controlling or controlled by or under direct or indirect common control with
the Company;

     WHEREAS, the Company wishes to supplement the Indenture to change certain
provisions of the Indenture as set forth below, and the Holders of a majority
of the aggregate principal amount of the outstanding Notes voting as a single
class as of June 25, 1998, excluding Notes owned by the Company, or by any
Person directly or indirectly controlling or controlled by or under direct or
indirect common control with the Company, have consented to the execution of
this Supplemental Indenture pursuant to the consent solicitation made by the
Company pursuant to that certain Consent Solicitation Statement, dated June 29,
1998, relating to the Notes (the "Consent Solicitation Statement"); and

     WHEREAS, the Company hereby covenants and represents that all things
necessary have been done to make this Supplemental Indenture a legal, valid and
binding agreement of the Company in accordance with the terms hereof and of the
Indenture.

     NOW THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the receipt of which is hereby acknowledged, it is
hereby agreed as follows:

                                  ARTICLE ONE

            DEFINITIONS AND OTHER PROVISIONS OF GENERAL APPLICATION

SECTION 101. Capitalized Terms.

     Capitalized terms used herein and not otherwise defined herein are used
with the respective meanings ascribed to such terms in the Indenture.


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SECTION 102. Effective Time.

     The amendments to the provisions of the Indenture provided for in this
Supplemental Indenture shall become operative and shall bind the parties hereto
when this Supplemental Indenture has been executed by the parties hereto (the
"Effective Time").

SECTION 103. Incorporation of Supplemental Indenture into Indenture.

     This Supplemental Indenture is executed by the Company and the Trustee
pursuant to the provisions of Section 9.02 of the Indenture, and the terms and
conditions hereof shall be deemed to be part of the Indenture for all purposes
at and as of the Effective Time. The Indenture, as amended and supplemented
by this Supplemental Indenture, is in all respects hereby adopted, ratified and
confirmed.

SECTION 104. Effect of Headings.

     The Article and Section headings herein are for convenience only and shall
not affect the construction hereof.

SECTION 105. Governing Law.

     The internal law of the State of New York shall govern and be used to
construe this Supplemental Indenture, without giving effect to applicable
principles of conflicts of law to the extent that the application of the laws of
another jurisdiction would be required thereby.

SECTION 106. Counterparts.

     This Supplemental Indenture may be executed in any number of counterparts,
each of which so executed shall be deemed to be an original, but all such
counterparts shall together constitute but one and the same instrument.

SECTION 107. Recitals.

     The recitals contained herein shall be taken as the statements of the
Company, and the Trustee assumes no responsibility for their correctness. The
Trustee makes no representations as to the validity or sufficiency of this
Supplemental Indenture.

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                                  ARTICLE TWO

                     AMENDMENTS TO PROVISIONS OF INDENTURE

Section 201.  DEFINITIONS.

     (a)  The definition of "Permitted Liens" contained in Section 1.01 of the
Indenture is hereby amended to read in its entirety as follows:

     "Permitted Liens" means, without duplication, each of the following:

          (i)     Liens in favor of the Company or any of its Wholly Owned
Restricted Subsidiaries;

          (ii)    Liens on property of a Person existing at the time such
Person is merged into or consolidated with the Company or any Restricted
Subsidiary of the Company, provided that such Liens were in existence prior to
the contemplation of such merger or consolidation and do not extend to any
assets other than those of the Person merged into or consolidated with the
Company or such Restricted Subsidiary;

          (iii)   Liens on property existing at the time of acquisition
thereof by the Company or any Restricted Subsidiary of the Company, provided
that such Liens were in existence prior to the contemplation of such
acquisition;

          (iv)    Liens existing on the date of this Indenture;

          (v)     Liens to secure the performance of statutory obligations,
surety or appeal bonds, performance bonds or other obligations of a like nature
incurred in the ordinary course of business;

          (vi)    Liens for taxes, assessments or governmental charges or
claims that are not yet delinquent or that are being contested in good faith by
appropriate proceedings promptly instituted and diligently concluded, provided
that any reserve or other appropriate provision as shall be required in
conformity with GAAP shall have been made therefor;

          (vii)   Liens securing Indebtedness of any Restricted Subsidiary of
the Company that does not exceed $5.0 million at any one time outstanding
represented by Capital Lease Obligations, mortgage financings or purchase money
obligations, in each case incurred for the purpose of financing all or any part
of the purchase price or cost of construction or improvement of property, plant
or equipment used in the business of such Restricted Subsidiary;

          (viii)  Liens on assets of Unrestricted Subsidiaries that secure
Non-Recourse Debt of Unrestricted Subsidiaries;


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          (ix)      Liens created pursuant to the Proceeds Pledge and Escrow
Agreement;

          (x)       Liens incurred in the ordinary course of business of the
Company or any Restricted Subsidiary of the Company with respect to obligations
that do not exceed $5.0 million at any one time outstanding and that (a) are not
incurred in connection with the borrowing of money or the obtaining of advances
or credit (other than trade credit in the ordinary course of business) and (b)
do not in the aggregate materially detract from the value of the property or
materially impair the use thereof in the operation of business by the Company or
such Restricted Subsidiary;

          (xi)      Liens securing the Notes;

          (xii)     easements, rights-of-way, zoning and similar restrictions
and other similar encumbrances or title defects which, in the aggregate, are not
material in amount, and which do not, in any case, materially detract from the
value of the property subject thereto (as such property is used by the Company
or any of its Restricted Subsidiaries) or interfere with the ordinary conduct of
the business of the Company or any of its Restricted Subsidiaries;

          (xiii)    Liens arising by reason of any judgment, decree or order or
any court so long as such Lien is adequately bonded and any appropriate legal
proceedings that may have been initiated for the review of such judgment, decree
or order shall not have been finally terminated or the period within which such
proceedings may be initiated shall not have expired;

          (xiv)     any interest or title of a lessor under any Capital Lease
Obligation;

          (xv)      Liens securing Indebtedness incurred pursuant to Section
4.09(b)(xii) hereof; and

          (xvi)     any extension, renewal or replacement, in whole or in part,
of any Permitted Lien, provided that any such extension, renewal or replacement
shall be no more restrictive in any material respects that the Lien so extended,
renewed or replaced and shall not extend to any additional property or assets.

SECTION 202.  Covenants.

     (a)     Section 4.09 of the Indenture is hereby amended to read in its
entirety as follows:

     SECTION 4.09  INCURRENCE OF INDEBTEDNESS AND ISSUANCE OF PREFERRED STOCK

          (a)       The Company shall not, and shall not permit any of its
     Subsidiaries to, directly or indirectly, create, incur, issue, assume,
     guarantee or otherwise become directly or indirectly liable, contingently
     or otherwise, with respect to (collectively, "incur") any Indebtedness
     (including Acquired Debt) and that the Company will not issue any
     Disqualified Stock and will not permit any of its Subsidiaries to issue any
     shares of preferred stock; provided, however, that the Company may incur
     Indebtedness (including Acquired


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Debt) and the Company may issue shares of Disqualified Stock if the Company's
Debt to Cash Flow Ratio would have been no greater than 5.5 to 1, in the case
of any such incurrence or issuance on or before December 31, 2000, or no
greater than 5.0 to 1, in the case of any such incurrence or issuance at any
time thereafter, in each case, determined on a pro forma basis (including a pro
forma application of the net proceeds thereof), as if the additional
Indebtedness had been incurred, or the Disqualified Stock had been issued, as
the case may be, at the beginning of the applicable four full fiscal quarter
period. The Company shall not incur any Indebtedness that is contractually
subordinated to any other Indebtedness of the Company unless such Indebtedness
is also contractually subordinated to the Senior Notes on substantially
identical terms; provided, however, that no Indebtedness of the Company shall be
deemed to be contractually subordinated to any other Indebtedness of the Company
solely by virtue of being unsecured.

     (b)  The provisions of Section 4.09(a) shall not apply to the incurrence
of any of the following items of Indebtedness (collectively, "Permitted Debt"):

          (i)  the incurrence by the Company or its Restricted Subsidiaries of
     Indebtedness under Credit Facilities; provided that the aggregate principal
     amount of all Indebtedness (with letters of credit being deemed to have a
     principal amount equal to the maximum potential liability of the Company
     thereunder) outstanding under all Credit Facilities after giving effect to
     such incurrence, including all Permitted Refinancing Indebtedness incurred
     to refund, refinance or replace any other Indebtedness incurred pursuant to
     this clause (i), does not exceed an amount equal to $40.0 million less the
     aggregate amount of all Net Proceeds of Asset Sales that have been applied
     since the date of this Indenture to repay Indebtedness under Credit
     Facilities (or any such Permitted Refinancing Indebtedness) pursuant to
     Section 4.10 hereof, provided, further, that the aggregate principal amount
     of Indebtedness at any one time outstanding under Credit Facilities that is
     incurred by, or secured by the Capital Stock or assets of, any Restricted
     Subsidiary that is located, or that derives substantially all of its
     revenue from the conduct of business, in Peru shall not exceed $15.0
     million;

          (ii)  the incurrence by the Company and its Restricted Subsidiaries of
     the Existing Indebtedness;

          (iii)   the incurrence by the Company of Indebtedness represented by
     the Notes;

          (iv)  the incurrence by the Company or any of its Restricted
     Subsidiaries of Indebtedness in connection with the acquisition of assets
     or a new Restricted Subsidiary, provided that such Indebtedness was
     incurred by the prior owner of such assets or such Subsidiary prior to such
     acquisition by the Company or such Restricted Subsidiary and was not
     Incurred in connection with, or in contemplation of, such acquisition by
     the Company or such Restricted Subsidiary: and provided

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further that the principal amount (or accreted value, as applicable) of such
Indebtedness (or accreted value, as applicable), including all Permitted
Refinancing Indebtedness incurred to refund, refinance or replace any other
Indebtedness incurred pursuant to this clause (iv), does not exceed $5.0 million
at any time outstanding;

     (v)  Indebtedness of the Company not to exceed, at any one time
outstanding, two times the sum of (A) the Current Market Value as of the date of
issue of any Qualified Capital Stock of the Company issued to the seller(s) of a
Permitted Business as consideration for the acquisition of such business and (B)
the net cash proceeds received by the Company after the date of this Indenture
from the issuance and sale of its Qualified Capital Stock to the extent that
such net cash proceeds have been, and continue to be, designated as Designated
Equity Proceeds to be used for the purpose of incurring additional Indebtedness
pursuant to this clause (v) as provided in the definition thereof; provided
that, to the extent that any such Qualified Capital Stock ceases to be
outstanding for any reason, any Indebtedness that was incurred as a result of
the receipt of net cash proceeds from the issuance of such Qualified Capital
Stock shall cease (as of the date on which such Qualified Capital Stock ceases
to be outstanding) to be permitted by virtue of this clause (v);

     (vi)  the incurrence by the Company or any of its Restricted Subsidiaries
of Permitted Refinancing Indebtedness in exchange for, or the net proceeds of
which are used to refund, refinance or replace Indebtedness (other than
intercompany Indebtedness or Indebtedness pursuant to a Credit Facility) that
was permitted by this Indenture to be incurred;

     (vii)  the incurrence by the Company or any of its Restricted Subsidiaries
of intercompany Indebtedness between or among the Company and any of its Wholly
Owned Restricted Subsidiaries; provided, however, that (A) if the Company is the
obligor on such Indebtedness, such Indebtedness is expressly subordinated to the
prior payment in full in cash of all Obligations with respect to the Senior
Notes and (B)(1) any subsequent issuance or transfer of Equity Interests that
results in any such Indebtedness being held by a Person other than the Company
or a Wholly Owned Restricted Subsidiary and (2) any sale or other transfer of
any such Indebtedness to a Person that is not either the Company or a Wholly
Owned Restricted Subsidiary shall be deemed, in each case, to constitute an
incurrence of such Indebtedness by the Company or such Restricted Subsidiary, as
the case may be;

     (viii)  the guarantee by the Company of Indebtedness of the Company or a
Restricted Subsidiary of the Company that was permitted to be incurred by
another provision of this covenant;

     (ix)  the incurrence by the Company's Unrestricted Subsidiaries of
Non-Recourse Debt; provided, however, that if any such Indebtedness ceases to be

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     Non-Recourse Debt of an Unrestricted Subsidiary, such event shall be deemed
     to constitute an incurrence of Indebtedness by a Restricted Subsidiary of
     the Company;

          (x)  Indebtedness of the Company or any Restricted Subsidiary of the
     Company (A) in respect of statutory obligations, performance, surety or
     appeal bonds or other obligations of a like nature incurred in the ordinary
     course of business or (B) under Hedging Obligations; provided that such
     agreements (1) are designed solely to protect the Company or its Restricted
     Subsidiaries against fluctuations in foreign currency exchange rates or
     interest rates and (2) do not increase the Indebtedness of the obligor
     outstanding at any time other than as a result of fluctuations in foreign
     currency exchange rates or interest rates or by reason of fees, indemnities
     and compensation payable thereunder;

          (xi)  the incurrence by the Company of additional Indebtedness in an
     aggregate principal amount (or accreted value, as applicable) at any time
     outstanding, including all Permitted Refinancing Indebtedness incurred to
     refund, refinance or replace any other Indebtedness incurred pursuant to
     this clause (xi), not to exceed $5.0 million; and

          (xii)  the incurrence by the Company and its Restricted Subsidiaries
     of Indebtedness in connection with the deposit by the Company and its
     Restricted Subsidiaries of funds with a financial institution and the
     onlending of such funds to, and the incurrence of such Indebtedness by, a
     Wholly Owned Restricted Subsidiary of the Company, provided that the
     principal amount of such Indebtedness does not exceed $100.0 million at any
     one time outstanding.

     (c)  For purposes of determining compliance with this covenant, in the
event that an item of Indebtedness meets the criteria of more than one of the
categories of Permitted Debt described in clauses (i) through (xi) of Section
4.09(b) hereof or is entitled to be incurred pursuant to Section 4.09(a)
hereof, the Company shall, in its sole discretion, classify such item of
Indebtedness in any manner that complies with this Section 4.09 and such item
of Indebtedness will be treated as having been incurred pursuant to only one of
such clauses of Section 4.09(b) hereof or pursuant to Section 4.09(a) hereof.
Accrual of interest and the accretion of accreted value will not be deemed to
be an incurrence of Indebtedness for purposes of this Section 4.09.

     (b)  Section 4.22 of the Indenture is hereby amended to read in its
entirety as follows:

SECTION 4.22. LIMITATION ON ISSUES AND SALES OF CAPITAL STOCK OF THE COMPANY.

     The Company shall not transfer, convey, sell, lease or otherwise dispose
of any Equity Interest of the Company to any Person unless the consideration
received therefor


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is at least equal to the Fair Market Value of such Equity Interests and all of
such consideration is in the form of cash.

        The provisions of the first paragraph of this section will not apply to:

        (i) the transfer, conveyance, sale, lease or other disposition of all or
   substantially all of the Equity Interests of the Company; provided that the
   transfer, conveyance, sale, lease or other disposition of all or
   substantially all of the Equity Interest of the Company will be governed by
   Section 4.15 and/or Section 5.01 hereof and not by the provisions of this
   section;

        (ii) the transfer, conveyance, sale, lease or other disposition of
   Equity Interests of the Company in exchange for long-term assets used or
   useful in a Permitted Business or a controlling interest in a Permitted
   Business; provided that the Company delivers to the Trustee (a) with respect
   to any such transfer, conveyance, sale, lease or other disposition or series
   of related transfers, conveyances, sales, leases or other dispositions
   involving Equity Interests with a fair market value less than $5.0 million, a
   resolution of the Board of Directors set forth in an Officers' Certificate
   certifying that such transfer, conveyance, sale, lease or other disposition
   is fair to the Company's shareholders and (b) with respect to any such
   transfer, conveyance, sale, lease, or other disposition or series of related
   transfers, conveyances, sales, leases or other dispositions involving Equity
   Interests with a fair market value equal to or in excess of $5.0 million, an
   opinion as to the fairness to the Company's shareholders of such transfer,
   conveyance, sale, lease or other disposition from a financial point of view
   issued by the Initial Purchaser or any other investment banking firm of
   national standing chosen by the Company;

        (iii) (A) the grant or issuance of options, warrants or other rights to
   acquire Capital Stock of the Company ("Options") pursuant to a stock option
   plan which (a) shall have been approved by the Company's stockholders, (b)
   shall prohibit the granting of Options prior to June 30, 1998 (other than to
   directors or employees of the Company or any Subsidiary of the Company
   appointed or hired subsequent to the date of this Indenture), (c) shall limit
   the aggregate number of shares of common stock of the Company issuable in any
   fiscal year upon the exercise of Options to 1.0 million (subject to
   adjustments for stock splits and other customary events) and (d) shall
   provide that any Option must have an exercise price equal to or in excess of
   the market price for the underlying common stock of the Company on the date
   such Option is granted by the Company and (B) the issuance of Capital Stock
   of the Company upon the exercise of any such Option; and

        (iv) the issuance of Capital Stock of the Company upon the exercise of
   any options or warrants to acquire Capital Stock of the Company outstanding
   on or prior to October 27, 1997.


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     IN WITNESS WHEREOF, the parties hereto have executed this Supplemental
Indenture as of the date first above written.

                                        STATE STREET BANK AND
                                        TRUST COMPANY, as Trustee

                                        By:  /s/ R Elovecky
                                            ---------------------------------
                                            Name: Rinette Elovecky
                                            Title: V.P.

                                        FIRSTCOM CORPORATION, as Issuer

                                        By:  /s/ Douglas G. Geib II
                                            ---------------------------------
                                            Name: Douglas G. Geib II
                                            Title: Chief Financial Officer


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