<PAGE>


                                                                 Exhibit 10.48

                            FIRST AMENDMENT TO LEASE
             (Substitution of Premises and Extension of Lease Term)

      THIS FIRST AMENDMENT TO LEASE ("Amendment") is executed as of June 29,
1999, between BAY COLONY CORPORATE CENTER LLC ("Landlord"), and LIONBRIDGE
TECHNOLOGIES, INC., a Delaware corporation ("Tenant").

                                    RECITALS

      A. Shorenstein Management, Inc., as Trustee of SRI Two Realty Trust, as
landlord, and Tenant, as tenant, entered into a written lease, dated February
13, 1997, pursuant to which Tenant leased from Landlord a portion of the fourth
(4th) floor of the building located at 950 Winter Street, Waltham, Massachusetts
(the "Building"). The lease was modified and supplemented by that certain letter
agreement, dated March 28, 1997, which confirmed the commencement date of the
lease, and that certain letter, dated January 29, 1999, pursuant to which the
address for notices to Landlord under the lease was changed. The lease, as so
modified and supplemented, is hereinafter referred to as the "Lease", and the
premises presently demised under the Lease are referred to herein as the
"Original Premises". The term of the Lease is scheduled to expire on February
28, 2001. Capitalized terms not otherwise defined herein shall have the meanings
given them in the Lease.

      B. Landlord and Tenant presently desire to amend the Lease to provide for
(i) the substitution of space on the second (2nd) floor of the Building for the
Original Premises, (ii) the construction by Landlord of certain improvements in
the new premises, (iii) the extension of the expiration date of the Lease to a
date that is approximately thirty-six (36) months from the date of such
substitution of premises, and (iv) certain other provisions agreed to by
Landlord and Tenant.

      NOW, THEREFORE, in consideration of the foregoing, Landlord and Tenant
hereby agree as follows:

      1. Extension of Lease Term. Effective as of the date hereof, the Lease
term set forth in Paragraph 2.b. of the Lease is extended for an additional
period commencing on March 1, 2001, and ending on the date that is the last day
of the thirty-sixth (36th) full calendar month after the Effective Date (as
defined in Paragraph 2.b. below).

      2. Substitution of Premises.

            a. Lease of Substitute Premises. From and after the Effective Date
(as defined below), those certain premises located on the second (2nd) floor of
the Building and outlined and labeled "Substitute Premises" on the attached
Exhibit A-1 (the "Substitute Premises") shall be substituted under the Lease for
the Original Premises, and thereupon all references in the Lease to the
"Premises" shall be deemed to refer to the Substitute Premises. The "Effective
Date" shall be the date on which Landlord Substantially Completes (as defined in
Paragraph 3.e. below) the Tenant Improvements (as defined in Paragraph 3.b.ii.
below) to be constructed by Landlord in the Substitute Premises pursuant to
Paragraph 3 below. The Effective Date shall be confirmed by the parties in
writing following Substantial Completion of the Tenant Improvements, as provided
in Paragraph 3 below.

            b. Deletion of Original Premises. Notwithstanding the substitution
of the Substitute Premises for the Original Premises, Tenant shall remain liable
for all of Tenant's rental and other obligations under the Lease with regard to
the Original Premises until such time as Tenant actually vacates and surrenders
the Original Premises to Landlord as required by Paragraph 4 below (the
"Surrender Date"); provided, however, that any and all obligations of Tenant
under the Lease that survive the expiration and termination of the Lease shall
survive the deletion of the Original Premises from the Lease with respect to
such obligations accruing prior to the later of such deletion or the Surrender
Date. Subject to the terms of the immediately preceding sentence and to payment
by Tenant of any accrued but unpaid Monthly Rent, Tenant's Electrical Charge,
Additional Rent and any other accrued but unpaid sums under the Lease with
respect to the Original Premises, Tenant shall have no further obligations under
the Lease with respect to the Original Premises from and after the date Tenant
so vacates the Original Premises.


                                       1
<PAGE>

      3. Improvements to Substitute Premises.

            a. Generally. Improvements shall be constructed in the Substitute
Premises by Landlord, through a contractor selected by Landlord (the
"Contractor"), pursuant to this Paragraph 3. Except as specifically provided in
this Paragraph 3, Tenant shall accept the Substitute Premises in their "as is"
condition, and Landlord shall have no obligation to make or pay for any
improvements or renovations in or to the Substitute Premises to prepare such
space for Tenant's occupancy, except as specifically provided in this Paragraph
3.

            b. Plans.

                  i. Promptly after execution of this Amendment by Landlord and
Tenant, Tenant shall furnish to Landlord for Landlord's review and approval
plans indicating the proposed location of walls and partitions in the Substitute
Premises or other conceptual or space plans of the improvements Tenant desires
in the Substitute Premises, together with such other plans and specifications as
are then available with respect to such improvements (the "Space Plans"),
prepared by an architect reasonably acceptable to Landlord ("Tenant's
Architect"). The Space Plans shall (A) show the general layout of all of the
improvements which Tenant desires to be constructed in the Substitute Premises,
and all such improvements shall comply with all applicable building codes and
other Legal Requirements (as defined in Paragraph 7.a.(16) of the Lease), (B)
include all applicable telephone and cable requirements, drywall, finish
specifications and special requirements, (C) separately note any proposed
structural work or extraordinary or supplemental electrical, plumbing or HVAC
requirements, and (D) contain such detail and specifications as would permit a
general contractor to obtain preliminary estimates of the cost of performing all
work shown thereon. The Space Plans and improvements shown thereon shall also
comply with the "Tenant Construction Standards" and "Conditions for
Construction" applicable to the Building (collectively, the "Building
Construction Standards"). The Space Plans shall identify any "long-lead"
materials (as described in Paragraph 3.f. below) then known by Tenant or
Tenant's Architect. Landlord shall respond to the Space Plans within ten (10)
days of its receipt thereof. Tenant shall respond promptly to any objections of
Landlord to the Space Plans and shall resubmit appropriately revised Space Plans
prepared by Tenant's Architect within five (5) days after Tenant's receipt of
Landlord's objections. The Space Plans, as finally approved in writing by
Landlord, shall be referred to herein as the "Final Space Plans."

                  ii. Final Plans. As soon as available following approval of
the Final Space Plans Tenant shall furnish to Landlord for Landlord's written
approval working plans and specifications (the "Working Drawings") prepared by
Tenant's Architect for all of the improvements which Tenant desires to be
constructed in the Substitute Premises. The Working Drawings shall show
improvements that conform to the Final Space Plans and the Building Construction
Standards, shall separately note any proposed structural work or extraordinary
or supplemental electrical, plumbing or HVAC requirements, and shall be in
sufficient detail as to enable the general contractor for the work to obtain all
necessary governmental permits for construction of all of the improvements and
to secure complete bids from qualified contractors to perform the work for all
of the improvements to be constructed in the Substitute Premises. Landlord shall
respond to the Working Drawings within ten (10) days of its receipt thereof.
Tenant shall respond promptly to any reasonable objections of Landlord to the
Working Drawings and shall resubmit appropriately revised Working Drawings
prepared by Tenant's Architect within five (5) days of Tenant's receipt of
Landlord's objections, and such resubmitted plans shall clearly indicate which
portions of the plans are revised and which portions of the plan remain
unchanged from the previously submitted plans. (The Working Drawings, as
approved in writing by Landlord, as revised by Tenant from time to time with
Landlord's written approval in accordance with the following provisions of this
Paragraph 3, are hereinafter called the "Final Plans", the improvements to be
performed in the Substitute Premises in accordance with the Final Plans are
hereinafter called the "Tenant Improvements". Tenant shall be responsible for
causing the Working Drawings to be completed (including Landlord's review and
approval, and Tenant's Architect's revisions of the Working Drawings, according
to the procedure and schedule set forth above) no later than June 15, 1999.

                  iii. Cooperation; No Release. Landlord and Tenant shall
cooperate with each other to resolve any space planning or other issues that are
raised by applicable local, state or federal building codes during the planning,
permit or construction process. Notwithstanding anything to the contrary
contained herein, Landlord's approval of any item reviewed by Landlord under
this Paragraph 3 shall merely indicate Landlord's consent to the proposed work
shown thereon, and in no event shall such consent by Landlord be deemed to
constitute a representation by Landlord that the work called for therein
complies with applicable building codes or other Legal Requirements nor shall
such consent release Tenant from Tenant's obligations to supply Space Plans,
Working Drawings and Final Plans that do so conform to applicable building codes
and Legal Requirements.

            c. Preparation of Budget and Revisions of Final Plans. Upon approval
of the Final Plans, the Contractor shall prepare a budget for the Tenant
Improvements and shall submit the same to Tenant. If Tenant disapproves of the
budget, then within three (3) days or Tenant's receipt thereof, Tenant shall so
notify Landlord and the Final Plans shall promptly be modified by the Architect,
in order to


                                       2
<PAGE>

satisfactorily reduce the cost of the work as shown on the budget. Any and all
revisions to the Final Plans shall be subject to Landlord's approval and at
Tenant's cost. Upon such revision of the Final Plans, Landlord shall cause the
Contractor to promptly prepare and submit to Tenant a revised estimated budget.
Tenant shall respond to the revised estimated budget in the manner described
above. Any delay in Substantial Completion (as defined in Paragraph 3.d. below)
of the Tenant improvements resulting from any revision to the Final Plans or the
budget shall constitute a Tenant Delay as defined in Paragraph 3.f. below. If
Tenant fails to raise any objections to the budget within the period described
above, Tenant shall be deemed to have approved the proposed budget.

            d. Changes. If Tenant shall desire any change, addition or
alteration in or to the Final Plans ("Change"), Tenant shall request that the
Architect prepare Working Drawings incorporating the requested Change; provided,
however, that Landlord reserves the right to reasonably disapprove any proposed
Change. If Landlord approves any proposed Change, Landlord shall give Tenant the
estimated cost of the Change and the estimated delay, if any, in Substantial
Completion of the Tenant Improvements, which will be caused by the Change.
Landlord will use reasonable care in preparing the estimates, but they shall be
estimates only and will not limit Tenant's obligation to pay for the actual cost
of the Change or be responsible for the delay resulting therefrom. Within two
(2) days after receipt of such cost and delay estimates, Tenant shall notify
Landlord in writing whether Tenant approves the Change. If Tenant approves the
Change, Landlord shall proceed with the Change. If the Change increases the cost
of the Tenant Improvements and the funds from the Allowance (as defined in
Paragraph 3.g. below) are not sufficient to pay for the Change, then Tenant
shall be liable for the additional cost, which cost shall be payable, at
Landlord's option, either prior to commencement of work on the Change or during
the course of construction. If the Change causes a delay in Substantial
Completion of the Tenant Improvements, Tenant's obligation to pay rent for the
Substitute Premises shall be accelerated as provided in Paragraph 3.f. below.
Within two (2) days after receipt of such cost and delay estimates, Tenant shall
notify Landlord in writing whether Tenant approves the Change. If Tenant fails
to approve the Change within such two (2) day period, construction of the Tenant
Improvements shall proceed as provided in accordance with the Final Plans as
they existed prior to the requested Change.

            e. Construction; Substantial Completion. Upon Tenant's approval of
the budget, Landlord shall cause the Contractor to promptly commence and
diligently pursue to completion construction of the Tenant Improvements. The
Contractor will provide ordinary power wiring to locations shown on the Final
Plans and shall provide and cause to be installed conduits to above ceiling line
from wall or floor outlets for Tenant's telephone and computer systems as shown
on the Final Plans, but shall in no event provide, install, pull or hook up such
wires, supply jacks or plugs or provide wiring necessary for special conditioned
power to the Substitute Premises. "Substantial Completion" of the Tenant
Improvements shall be deemed to have occurred when they have been completed
pursuant to the Final Plans, subject only to the completion or correction of
Landlord's Punch List Items. Punch List Items shall mean incomplete or defective
work or materials in the improvements called for in the Final Plans which do not
materially impair Tenant's use of the Substitute Premises for the conduct of
Tenant's business therein.


                                       3
<PAGE>

            f. Tenant Delays. If the Effective Date is delayed as a result of
(i) the failure of Tenant to submit Space Plans, Working Drawings or Final Plans
to Landlord by the dates or within the time periods set forth in Paragraph 3.b.
above, (ii) any Changes requested by Tenant in the Tenant Improvements shown on
the Final Plans (including any cost or delay resulting from proposed changes
that are not ultimately made), (iii) any failure by Tenant to timely pay any
amounts due from Tenant hereunder, including any additional costs resulting from
any Change (it being acknowledged that if Tenant fails to make or otherwise
delays making such payments, Landlord may stop work on the Tenant Improvements
rather than incur costs which Tenant is obligated to fund but has not yet done
so and any delay from such a work stoppage will be a Tenant Delay), (iv) the
inclusion in the Tenant Improvements of any so-called "long lead" materials
(such as fabrics, panellings, tiling, carpeting, light fixtures, HVAC equipment
or other items that must be imported or are of unusual character or limited
availability), (v) any delay by Tenant in responding to inquiries regarding the
construction of the Tenant Improvements or in granting Tenant's approval of
materials or finishes for the Tenant Improvements, or (vi) any other delay
requested or caused by Tenant, then the date of commencement of Tenant's
obligation to pay rent for the Substitute Premises, as set forth in Paragraphs 5
and 6 below, shall be accelerated by the number of days of such delay. In no
event shall Landlord be liable to Tenant for any delay in completion of the
Tenant Improvements shown on the Final Plans caused or occasioned by strikes,
lockouts, labor disputes, shortages of material or labor, fire or other
casualty, acts of God or any other cause.

            g. Cost of Tenant Improvements. Landlord shall bear the entire cost
of Landlord's Work, as provided in Paragraph 3.h. below. Further, Landlord shall
bear the cost of construction of the Tenant Improvements (including
architectural and design costs and the Contractor's fees, and Landlord's
supervision fee of five percent (5%) of the total coat of construction), limited
however to a maximum expenditure by Landlord for the Tenant Improvements of
Seventy Eight Thousand Seven Hundred Ninety Dollars ($78,790.00) (the
"Allowance"). Tenant shall pay for all costs of the design and construction of
the Tenant Improvements which are in excess of the Allowance (collectively, the
"Excess Cost"), which Excess Cost shall be paid by Tenant to Landlord, within
twenty (20) days of written demand, which demand may be for payment in advance
or in course-of-construction installments. No portion of the Allowance may be
applied to the purchase of signage, trade fixtures, equipment, furniture,
consultants' fees, free rent or any other costs other than design and
construction costs due under the terms of this Amendment.

            h. Landlord's Work. Landlord shall bear the entire cost of (i)
demising the Substitute Premises, (ii) demolishing the existing demising wall
between the eastern and western sections of the Substitute Premises, (iii)
demolishing those interior walls in the western section of the Substitute
Premises as indicated on the Final Plans, and (iv) supplying and installing (in
locations designated by Tenant and approved by Landlord) the dishwasher, sink
and cabinets presently located in the kitchen area of the premises located to
the immediate north of the Substitute Premises. The foregoing is collectively
referred to herein as "Landlord's Work." In no event shall Landlord be liable to
Tenant for any delay in completion of any of Landlord's Work occasioned by
strikes, lockouts, labor disputes, shortages of material or labor, fire or other
casualty, acts of God or other causes.

      4. Surrender of Original Premises. Tenant shall surrender the Original
Premises to Landlord within ten (10) business days after the date on which the
Tenant Improvements in the Substitute Premises have been Substantially
Completed. The Original Premises shall be surrendered by Tenant in the condition
required by Paragraph 20.a. of the Lease. All costs of moving Tenant's
furnishings and equipment (including relocation and/or installation of voice and
data cabling) out of the Original Premises and into the Substitute Premises
shall be borne by Tenant.

      5. Monthly Rent for Substitute Premises. To reflect the lease of the
Substitute Premises, effective as of the Effective Date, Monthly Rent under
Paragraphs 2.c. and 5 of the Lease shall be payable for the Substitute Premises
in the amount of Twenty One Thousand Ten and 67/100 Dollars ($21,010.67) per
month.

      6. Tenant's Share. Base Year, Base Tax Year, and Tenant's Electrical
Charge for Substitute Premises. To reflect the lease of the Substitute Premises,
effective as of the Effective Date: (a) the Tenant's Share set forth in
Paragraph 2.e. of the Lease shall be 2.87%, (b) the Base Year set forth in
Paragraph 2.f. of the Lease shall be calendar year 1999, (c) the Base Tax Year
set forth in Paragraph 2.f, of the Lease shall be the fiscal tax year ending
June 30, 2000, and (d) the Tenant's Electrical Charge set forth in Paragraph
2.i. of the Lease shall be Six Hundred Twenty-Three and 75/100 Dollars ($623.75)
per month.

      7. Retention of Existing Security Deposit. To reflect the lease of the
Substitute Premises, effective as of the date hereof, the final grammatical
paragraph of Paragraph 6 of the Lease, regarding Landlord's return of a portion
of the Security Deposit required under Paragraph 2.d. of the Lease after the
first anniversary of the Commencement Date of the Lease, shall be deleted.

      8. Real Estate Brokers. Tenant represents and warrants that it has
negotiated this Amendment directly with Shorenstein Management, Inc., and has
not authorized or employed, or acted by implication to authorize or to employ,
any other real estate broker or salesman to act for Tenant in connection with
this Amendment. Tenant shall indemnify, defend and hold Landlord harmless from
and against any and all Claims by any real estate broker or salesman other than
Shorenstein Management, Inc.


                                       4
<PAGE>

for a commission, finder's fee or other compensation as a result of Tenant's
entering into this Amendment.

      9. Lease in Full Force and Effect. Except as provided above, the Lease is
unmodified hereby and remains in full force and effect.

      10. Authority. If Tenant is a corporation, partnership, trust, association
or other entity, Tenant and each person executing this Amendment on behalf of
Tenant hereby covenants and warrants that (a) Tenant is duly incorporated or
otherwise established or formed and validly existing under the laws of its state
of incorporation, establishment or formation, (b) Tenant has and is duly
qualified to do business in the state in which the Real Property is located, (c)
Tenant has full corporate, partnership, trust, association or other appropriate
power and authority to enter into this Amendment and to perform all Tenant's
obligations under the Lease, as amended by this Amendment, and (d) each person
(and all of the persons if more than one signs) signing this Amendment on behalf
of Tenant is duly and validly authorized to do so.


                                       5
<PAGE>

      11. No Offer. Submission of this instrument for examination and signature
by Tenant does not constitute an offer to lease or to amend the Lease, or an
reservation of or option for lease or to amend the Lease, and is not effective
as a lease amendment or otherwise until execution and delivery by both Landlord
and Tenant.


      IN WITNESS WHEREOF, the parties hereto have executed this document as of
the date and year first above written.

Landlord:                                          Tenant:

BAY COLONY CORPORATE CENTER LLC,                LIONBRIDGE TECHNOLOGIES, INC.
a Delaware limited liability company               a Delaware corporation


By   Shorenstein Realty Investors Two, L.P,.       By: /s/ Stephen Lifshatz
     a California limited partnership,                 -------------------------
     Member                                        Name: Stephen Lifshatz
                                                        ------------------------
     By   SRI Investors Two, L.P.,                 Title: CFO
          a California limited partnership,              -----------------------
          General Partner

          By   Shorenstein Company, L.P., a
               California limited partnership,
               General Partner

               By   Shorenstein Management, Inc., a
                    California corporation,
                    General Partner

                    By __________________________________
                       Douglas W. Shorenstein
                       President


                                       6