Document:

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                                                                   EXHIBIT 10.19
                             EMPLOYMENT AGREEMENT

     This Employment Agreement ("Agreement"), executed this _______ day of
_______ 1999 to be effective as of January 1, 2000, is between AMERICAN
TELESOURCE INTERNATIONAL, INC., a Delaware corporation (the "Employer"), and H.
Douglas Saathoff ("Employee").

                               R E C I T A L S:

     F.   The Employer and Employee entered into an Executive Employment
          Agreement dated effective January 1, 1997 for a period of three years.

     G.   The Employer decided not to renew the Executive Employment Agreement,
          and has given notice to Employee that the Executive Employment
          Agreement will not renew and will therefore terminate effective
          December 31, 1999.

     H.   The Employer and Employee agreed to enter into a new employment
          agreement for a one year term on the terms and conditions herein
          provided.

     I.   The Employer considers the maintenance of a sound management team,
          including Employee, essential to protecting and enhancing its best
          interests and those of its stockholders.

     J.   Employee will be an officer of the Employer and Employee will be a
          member of Employer's management team.

     NOW, THEREFORE, in consideration of the Employer's agreement to employ
Employee pursuant to the terms of this Agreement and Employee's future
employment with Employer, and other good and valuable consideration, the parties
agree as follows:

     Section 1.  Employment.  The Employer hereby employs Employee, and Employee
hereby accepts employment, upon the terms and subject to the conditions stated
in this Agreement.

     Section 2.  Duties.  Employee shall be employed as Chief Financial Officer
of the Employer,  or such other positions with Employer to which he may be
appointed by the Board of Directors of the Employer (the "Board").  It is
understood that Employee may be requested from time to time to provide
assistance or services to, or act as an officer or director of  the Employer or
any of its subsidiaries or other affiliates.   Employee shall perform such
services and, if elected as a director or officer of any such company, shall
hold such office (and discharge its duties) without additional compensation
other than the compensation set forth in this Agreement; provided, however, that
this Agreement does not prohibit (or require) the affiliates of Employer from
offering additional compensation. Employee agrees to devote his full work time
and best efforts to the performance of the duties as an Employee of Employer and
to the performance of such other duties as assigned him from time to time by the
Board or the Chairman of the Board.

     Section 3.  Term.  The initial term of employment of Employee hereunder
shall continue for one year, from January 1, 2000 ("Employment Date")  until
December 31, 2000, unless earlier terminated pursuant to Section 6 herein.

     Section 4.  Compensation and Benefits.  In consideration for the services
of Employee hereunder, the Employer shall compensate Employee as follows:

     (a)  Base Salary.  Until the termination of Employee's employment
hereunder, Employer shall pay Employee a base salary at the rate of at least
$2014.15 per week ("Base Salary"), payable in accordance with the regular
payroll practices of the Employer for executives, less such deductions or
amounts as are required to be deducted or withheld by applicable laws or
regulations and less such other deductions or amounts, if any, as are authorized
by Employee. The Base Salary may not be decreased at any time during the term of
Employee's employment hereunder Any increase in Base Salary shall be in the sole
discretion of the Compensation Committee of the Board.
<PAGE>

     (b)  Executive Bonus Plan.  Employee shall be eligible to receive from the
Employer such  management incentive bonuses as may be provided in management
incentive bonus plans adopted from time to time by Employer.

     (c)  Vacation.  Employee shall be entitled time off in accordance with the
Employee's vacation and absence policy, as it may be modified from time to time
during Employee's employment hereunder, provided that Employee will have no less
than four (4) weeks of paid vacation during the initial term of this Agreement,
and each subsequent year if the initial term is extended.

     (d)  Life Insurance Benefits.  Employer shall pay the premiums allocable to
a term life insurance policy in the face amount of $150,000 covering Employee as
the named insured, subject to Employee's passing a standard physical examination
in order to permit issuance of the policy at standard (non-rated) premiums and
satisfaction of any other standard underwriting requirements.  Employee shall be
the owner of such policy and shall have the right to designate the beneficiary
of the policy proceeds.  Employee shall be liable for income taxes with respect
to premium amounts includable in Employee's taxable income.

     (e)  Group Insurance Benefits.  Employee shall be entitled to participate
in the Employer's group health and disability programs as are made available to
the Employer's other executives and officers and the Employee's participation in
such programs shall be at the same rates which are available to the Employer's
other executives and officers.

     (f)  Savings Plans.  Employee shall be entitled to participate in
Employer's 401(k) plan, or other retirement or savings plans as are made
available to the Employer's other executives and officers on the same terms
which are available to the Employer's other executives and officers;

     (g)  Health Club Membership.  Employer shall pay for or reimburse Employee
for a family membership at a health and fitness club of Employee's choosing,
provided that the total cost of the membership does not exceed $75 per month.

     Section 5.  Expenses.  The parties anticipate that in connection with the
services to be performed by Employee pursuant to the terms of this Agreement,
Employee will be required to make payments for travel, entertainment of business
associates and similar expenses.  Employer shall reimburse Employee for all
appropriate and reasonable expenses authorized by Employer and incurred by
Employee in the performance of his duties hereunder.  Employee shall comply with
such budget limitations and approval and reporting requirements with respect to
expenses as Employer may establish from time to time.

     Section 6.  Termination.

     (a)  General.  Employee's employment hereunder shall commence on the
Employment Date and continue until the end of the term specified in Section 3,
except that the employment of Employee hereunder shall terminate prior to such
time in accordance with the following:

          (i)  Death or Disability.  Upon the death of Employee during the term
     of his employment hereunder or, at the option of Employer, in the event of
     Employee's Disability, upon 30 days' notice to Employee.  "Disability" with
     respect to an Employee shall be deemed to exist if the Employee meets the
     definition of either "disabled" or "disability" under the terms of the
     Employer's long-term disability benefit program (including the definitions
     for total or partial disability). Any refusal by Employee to submit to a
     reasonable medical examination to determine whether Employee is so disabled
     shall be deemed  to constitute conclusive evidence of Employee's
     disability.

          (ii) For Cause.  For "Cause" immediately upon written notice by
     Employer to Employee.  A termination shall be for "Cause" if:

          (7)       Employee commits fraud, bribery, embezzlement or other
               material dishonesty with the respect to the business of Employer,
               or Employer discovers that Employee has committed any such act in
               the past with respect to a previous employer; or
<PAGE>

          (8)       Employee commits a felony or any criminal act involving
                 moral turpitude or Employer discovers that Employee has
                 committed any such act in the past; or

          (9)       Employee commits a material breach of any of the covenants,
                 representations, terms or provisions hereof; or

          (10)      Employee violates any instructions or policies of Employer
                 with respect to the operation of its business or affairs or
                 Employee fails to obey written directions delivered to Employee
                 by the Employer's Board or Chairman of the Board; or

          (11)      Employee commits or omits to perform any act the performance
                 of which or the omission of which constitutes substantial
                 failure of Employee to diligently and effectively perform his
                 duties to Employer or adversely affects or could adversely
                 affect the Employer's business reputation; or

          (12)      Employee uses illegal drugs.

          (iii)  Without Cause.  Without Cause immediately upon notice by
     Employer to Employee.

     (b)  Severance Pay.

          (i)    Termination Upon Death or Disability or For Cause. Employee
     shall not be entitled to any severance pay or other compensation upon
     termination of his employment pursuant to Section 6(a)(i) or (ii) except
     for his Base Salary accrued but unpaid as of the date of termination,
     unpaid expense reimbursements under Section 5 for expenses incurred in
     accordance with the terms hereof prior to termination, compensation for
     accrued, unused vacation as of the date of termination ("Accrued Amounts"),
     and in the event of termination pursuant to Section 6(a)(i) for Disability,
     an amount equal to twenty-six times the difference between the Base Salary
     in effect at the time of termination and twenty-six weeks' worth of
     benefits to be paid under the Employer's long term disability plan. This
     amount shall be paid in a lump sum no later than ten (10) business days
     following the date of Employee's termination.

          (ii)   Termination Without Cause.  In the event Employee's employment
     hereunder is terminated pursuant to Section 6(a)(iii) prior to the
     expiration of the initial term of this Agreement (as such initial term may
     have been extended), Employer shall pay Employee, as consideration for the
     execution of a separation and release agreement and in lieu of any further
     compensation payable hereunder other than Accrued Amounts, a cash amount
     equal to twenty-six (26) times Employee's then current Base Salary.  Such
     separation payment shall be Employee's sole remedy in connection with such
     termination.  The Separation payment shall be made as specified above
     without regard to the number of months remaining in the term of this
     Agreement, and shall be paid within ten (10) business days of the
     Employee's execution of a separation and release agreement.

     (c)  Change in Control.  If a "Change in Control" occurs during Employee's
employment under this Agreement, and if Employee's employment is terminated
"Without Cause" pursuant to Section 6(a)(iii) above prior to the end of a period
of twenty-four (24) months beyond the month in which a "Change in Control" of
the Employer occurs, or if Employee voluntarily terminates his employment prior
to the end of a period three (3) months beyond the month in which a Change in
Control of the Employer occurs, Employee shall receive  the amount determined
pursuant to Section 6(b)(ii) above.  A "Change in Control" of Employer shall be
deemed to have occurred if (i) any "person" or "group" (as such terms are used
in Sections 13(d) and 14(d) of the Securities Exchange Act of 1934, as amended
(the "Act")), becomes the "beneficial owner" (as such term is defined in Rule
13d-3 under the Act), directly or indirectly, of outstanding securities of
Employer representing 40% of more of the combined voting power of the
outstanding securities of the Employer, or (ii) during any period of two
consecutive years, individuals who at the beginning of such period constitute
the Board cease for any reason to constitute a majority of the Board (except
that any new director who is elected by the Board to fill a vacancy created by
the death, resignation or disqualification of a member of the Board shall not be
considered a new member of the Board for purposes of this definition), or (iii)
the shareholders of Employer approve (A) a merger or consolidation of Employer
with any other entity, other than a merger or consolidation which would result
in the voting securities of
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Employer outstanding immediately prior thereto continuing to represent (either
by remaining outstanding or by being converted into voting securities of the
surviving entity) at least 60% of the combined voting power of the voting
securities of Employer, or (B) a plan of complete liquidation of Employer, or
(C) an agreement or agreements for the sale or disposition, in a single
transaction or series of related transactions, by the Employer of all or
substantially all of the property and assets of Employer.

Section 7.  Inventions; Assignment.

     (a)  Inventions Defined.  All rights to discoveries, inventions,
improvements, designs and innovations (including all data and records pertaining
thereto) that relate to the business of Employer, including its affiliates,
whether or not able to be patented, copyrighted or reduced to writing, that
Employee may discover, invent or originate during the term of his employment
hereunder, and for a period of six months thereafter, either alone or with
others and whether or not during working hours or by the use of the facilities
of Employer ("Inventions"), shall be the exclusive property of Employer.
Employee shall promptly disclose all Inventions to Employer, shall execute at
the request of Employer any assignments or other documents Employer may deem
necessary to protect or perfect its rights therein, and shall assist Employer,
at Employer's expense, in obtaining, defending and enforcing Employer's rights
therein.  Employee hereby appoints Employer as his attorney-in-fact to execute
on his behalf any assignments or other documents deemed necessary by Employer to
protect or perfect its rights to any Inventions.

     (b)  Covenant to Assign and Cooperate.  Without limiting the generality of
the foregoing, Employee shall assign and transfer to Employer the world-wide
right, title and interest of Employee in the Inventions.  Employee agrees that
Employer may apply for and receive patent rights (including Letters Patent in
the United States) for the Inventions in Employer's name in such countries as
may be determined solely by Employer.  Employee shall communicate to Employer
all facts known to Employee relating to the Inventions and shall cooperate with
Employer's reasonable requests in connection with vesting title to the
Inventions and related patents exclusively in Employer and in connection with
obtaining, maintaining and protecting Employer's exclusive patent rights in the
Inventions.

     (c)  Successors and Assigns.  Employee's obligations under this Section 7
shall inure to the benefit of Employer, its affiliates and their respective
successors and assigns and shall survive the expiration of the term of this
Agreement for such time as may be necessary to protect the proprietary rights of
Employer and its affiliates in the Inventions.

     Section 8.  Confidential Information.

     (a)  Acknowledgment of Proprietary Interest.  Employee acknowledges the
proprietary interest of Employer and its affiliates in all Confidential
Information (as defined below).  Employee agrees that all Confidential
Information learned by Employee during his employment with Employer or
otherwise, whether developed by Employee alone or in conjunction with others or
otherwise, is and shall remain the exclusive property of Employer.  Employee
further acknowledges and agrees that his disclosure of any Confidential
Information will result in irreparable injury and damage to Employer.

     (b)  Confidential Information Defined. "Confidential Information" means all
trade secrets, copyrightable works, confidential or proprietary information of
Employer or its affiliates, including without limitation, (i) information
derived from reports, investigations, experiments, research and work in
progress, (ii) methods of operation, (iii) market data, (iv) proprietary
computer programs and codes, (v) drawings, designs, plans and proposals, (vi)
marketing and sales programs, (vii) the identities of clients or customers ,
(viii) historical financial information and financial projections, (ix) pricing
formulae and policies, (x) all other concepts, ideas, materials and information
prepared or performed for or by Employer and (xi) all information related to the
business, services, products, purchases or sales of Employer or any of its
suppliers and customers, other than information that is publicly available.
<PAGE>

     (c)  Covenant Not To Divulge Confidential Information. Employer is entitled
to prevent the disclosure of Confidential Information. As a portion of the
consideration for the employment of Employee and for the compensation being paid
to Employee by Employer, Employee agrees at all times during the term of his
employment hereunder and thereafter to hold in strict confidence and not to
disclose or allow to be disclosed to any person, firm or corporation, other than
to persons engaged by Employer to further the business of Employer, and not to
use except in the pursuit of the business of Employer, the Confidential
Information, without the prior written consent of Employer.

     (d)  Return of Materials at Termination. In the event of any termination or
cessation of his employment with Employer for any reason, Employee shall
promptly deliver to Employer all documents, data and other information derived
from or otherwise pertaining to Confidential Information. Employee shall not
take or retain any documents or other information, or any reproduction or
excerpt thereof, containing or pertaining to any Confidential Information.

     Section 9.   Non-Solicitation.

     (a)  Solicitation of Employees.  During Employee's employment with Employer
and for a period of twelve (12) months after termination of such employment at
any time and for any reason, and regardless of whether any payments are made to
Employee under this Agreement as a result of such termination, Employee shall
not solicit, participate in or promote the solicitation of any person who was
employed by Employer or any of its affiliates at the time of Employee's
termination of employment with Employer to leave the employ of Employer or any
of its affiliates, or, on behalf of himself or any other person, hire, employ or
engage any such person.  Employee further agrees that, during such time, if an
employee of Employer or any of its affiliates contacts Employee about
prospective employment, Employee will inform such employee that he or she cannot
discuss the matter further without the consent of Employer (and the applicable
affiliate).

     (b)  Solicitation of Clients, Customers, Etc.  During Employee's employment
with Employer and for a period of twelve (12) months after termination of
Employee's employment at any time and for any reason, and regardless of whether
any payments are made to Employee under this Agreement as a result of such
termination, Employee shall not, directly or indirectly, solicit any person who,
at the time of termination of Employee's employment with Employer, was a client,
customer, policyholder, vendor, consultant or agent of Employer or its
affiliates to discontinue business, in whole or in part, with Employer or its
affiliates.  Employee further agrees that, during such time, if such a client,
customer, policyholder, vendor, or consultant or agent contacts Employee about
discontinuing business with Employer or moving that business elsewhere, Employee
will inform such client, customer, policyholder, vendor, consultant or agent
that he or she cannot discuss the matter further without the consent of Employer
(and the applicable affiliate).

     Section 10.  No-Compete.

     (a)  Competition During Employment. Employee agrees that during the term of
his employment with Employer, neither he nor any of his affiliates, will
directly or indirectly compete with Employer or its affiliates in any way, and
that he will not act as an officer, director, employee, consultant, shareholder,
lender, or agent of any entity which is engaged in any business of the same
nature as, or in competition with, the businesses in which Employer and its
affiliates are now engaged or in which Employer or its affiliates become engaged
during the term of employment; provided, however, that this Section 10(a) shall
not prohibit Employee or any of his affiliates from: (i) purchasing or holding
an aggregate equity interest of up to 1%, so long as Employee and his affiliates
combined do not purchase or hold an aggregate equity interest of more than 5%,
in any business in competition with Employer and its affiliates. Furthermore,
Employee agrees that during the term of employment, he will undertake no
planning for the organization of any business activity competitive with the work
he performs as an employee of Employer and Employee will not combine or conspire
with any other employees of Employer and its affiliates for the purpose of the
organization of any such competitive business activity.

     (b)  Competition Following Employment. In order to protect Employer against
the unauthorized use or the disclosure of any Confidential Information of
Employer and its affiliates presently known or hereinafter obtained by Employee
during his employment under this Agreement, Employee agrees that for a period of
twelve (12) months after the termination or cessation of his employment with
Employer at any time and for any reason, and regardless of whether any payments
are made to Employee under this Agreement as a result of such termination,
<PAGE>

neither Employee nor any of his affiliates, shall, directly or indirectly, for
itself or himself or on behalf of any other corporation, person, firm,
partnership, association, or any other entity (whether as an individual, agent,
servant, employee, employer, officer, director, shareholder, investor,
principal, consultant or in any other capacity):

               (i)   engage or participate in any business which engages in
         competition with such businesses being conducted by Employer or any of
         its affiliates during the term of employment anywhere in any state in
         the United States or in any foreign country where the Employer or any
         of its affiliates provides telecommunications services, including,
         without limitation, domestic and international call services or
         domestic and international telecommunications networks of voice, data,
         fax or video transmission to or from the United States and Latin
         America or within Latin America, or any other business in which the
         Employer or any of its affiliates has been actively engaged during the
         term Employee performed services for the Employer; provided, however,
         that this provision shall not prohibit Employee or any of his
         affiliates from purchasing or holding an aggregate equity interest of
         up to 1%, so long as Employee and his affiliates combined do not
         purchase or hold an aggregate equity interest of more than 5%, in any
         business in competition with Employer;

               (ii)  assist or finance any person or entity in any manner or in
         any way inconsistent with the intents and purposes of this Agreement.

     Section 11.  General.

     (a)  Notices.  All notices and other communications hereunder shall be in
writing or by written telecommunication, and shall be deemed to have been duly
given if delivered personally or if mailed by certified mail, return receipt
requested or by written telecommunication, to the relevant address set forth
below, or to such other address as the recipient of such notice or communication
shall have specified to the other party in accordance with this Section 11(a):

     If to Employer, to:

     American TeleSource International, Inc.
     12500 Network Boulevard, Suite 407
     San Antonio, Texas, 78249
     Attention: Chairman of the Board
      (or the subsequent headquarters of Employer as known to Employee)

     If to Employee, to the Employee's last known address appearing on
     Employer's records

     (b)  Withholding.  All payments required to be made to Employee by
Employer under this Agreement shall be subject to the withholding of such
amounts, if any, relating to federal, state and local taxes as may be required
by law.

     (c)  Equitable Remedies.  Each of the parties hereto acknowledges and
agrees that upon any breach by Employee of his obligations under any of Sections
7, 8, 9, and 10 Employer shall suffer immediate, great and irreparable injury
and shall have no adequate remedy at law.   Accordingly, in event of such
breach,  Employer shall be entitled, in addition to other remedies and without
showing actual damages, to specific performance and other appropriate injunctive
and equitable relief.

     (d)  Severability.  If any provision of this Agreement is held to be
illegal, invalid or unenforceable, such provision shall be fully severable, and
this Agreement shall be construed and enforced as if such illegal, invalid or
unenforceable provision never comprised a part hereof, and the remaining
provisions hereof shall remain in full force and effect and shall not be
affected by the illegal, invalid or unenforceable provision or by its severance.
Furthermore, in lieu of such illegal, invalid or unenforceable provision, there
shall be added automatically as part of this Agreement a provision as similar in
its terms to such illegal, invalid or unenforceable provision as may be possible
and be legal, valid and enforceable.
<PAGE>

     (e)  Waivers. No delay or omission by either party in exercising any right,
power or privilege hereunder shall impair such right, power or privilege, nor
shall any single or partial exercise of any such right, power or privilege
preclude any further exercise thereof or the exercise of any other right, power
or privilege.

     (f)  Counterparts. This Agreement may be executed in multiple counterparts,
each of which shall be deemed an original, and all of which together shall
constitute one and the same instrument.

     (g)  Captions.  The captions in this Agreement are for convenience of
reference only and shall not limit or otherwise affect any of the terms or
provisions hereof.

     (h)  Interpretation of Agreement.  This Agreement shall be construed
according to its fair meaning and not for or against either party.  Use of the
words "herein," "hereof," "hereto," "hereunder" and the like in this Agreement
refer to this Agreement only as a whole and not to any particular section or
subsection of this Agreement, unless otherwise noted.  The masculine gender
shall be deemed to denote the feminine or neuter genders, the singular to denote
the plural, and the plural to denote the singular, where the context so permits.

     (i)  Binding Agreement; Assignment.  This Agreement shall be binding upon
and inure to the benefit of the parties and shall be enforceable by the personal
representatives and heirs of Employee and the successors and assigns of
Employer.  The affiliates of Employer shall be considered third party
beneficiaries of this Agreement with respect to any services provided by
Employee to them and in connection with Employee's covenants in Sections 7,8,9
and 10 hereof.  This Agreement may be assigned by the Employer; provided that in
the event of any such assignment, the Employer shall remain liable for all of
its obligations hereunder and shall be liable for all obligations of all such
assignees hereunder.  If Employee dies while any amounts would still be payable
to him hereunder, such amounts shall be paid to Employee's estate.  This
Agreement is not otherwise assignable by Employee.

     (j)  Entire Agreement.  This Agreement contains the entire understanding of
the parties, supersedes all prior agreements and understandings relating to the
subject matter hereof and may not be amended except by a written instrument
hereafter signed by each of the parties hereto.

     (k)  Governing Law.  This Agreement and the performance hereof shall be
construed and governed in accordance with the laws of the State of Texas,
without regard to its choice of law principles.

     (l)  Arbitration.  Without limiting Employer's right to seek equitable
remedies under Section 11(c) above,  Employer and Employee agree that any
dispute or controversy arising under or in connection with this Agreement shall
be settled by arbitration.  Arbitration under this Agreement shall be governed
by the Federal Arbitration Act and proceed in San Antonio, Texas in accordance
with the rules of the American Arbitration Association ("AAA").  Arbitration
will be conducted before a panel of three neutral arbitrators selected from a
AAA list of proposed arbitrators with business law experience.  Either party may
take any legal action needed to protect any right pending completion of the
arbitration.  The arbitrator will determine whether an issue is arbitrable and
will give effect to applicable statutes of limitation.  The arbitrator has the
discretion to decide, upon documents only or with a hearing, any motion to
dismiss for failure to state a claim or any motion for summary judgment.
Discovery shall be governed by the Federal Rules of Civil Procedure and the
Federal Rules of Evidence.  All information developed by the arbitration or
litigation shall be held in confidence subject to such protective orders as the
arbitrator deems useful to ensure complete confidentiality. The decision of the
arbitrator shall be final and binding on all parties to this Agreement, and
judgment thereon may be entered in any court having jurisdiction over the
parties.  All costs of the arbitration proceeding or litigation to enforce the
arbitration award shall be paid by the party against whom the arbitrator
decides.

     (m)  Employee Representations.   Employee represents and certifies to
Employer that he: (i) has received a copy of this Agreement for review and
study and has had ample time to review it before signing; (ii) has read this
Agreement carefully; (iii) has been given a fair opportunity to discuss and
negotiate the terms of this Agreement; (iv) understands its provisions; (v) has
had the opportunity to consult his attorney; (vi) has determined that it is in
his best interest to enter into his Agreement; (vii) has not been influenced to
sign this Agreement by any statement or representation by Employer or its
counsel not contained in this Agreement; and (viii) enters into this Agreement
knowingly and voluntarily.
<PAGE>

EXECUTED as of the date and year first above written.

                          AMERICAN TELESOURCE INTERNATIONAL, INC.

                              By  /s/ Arthur L. Smith
                                  -------------------
                                  Chairman of Board of Directors

                                  /s/ H. Douglas Saathoff
                              ---------------------------
                                    H. Douglas Saathoff<PAGE>

                                                                   Exhibit 10.23
COMMERCIAL LEASE

                       ARTICLE 1.00 - BASIC LEASE TERMS

     1.01  Parties. This lease agreement ("Lease") is entered into by and
between the following Lessor and Lessee:

     ACLP University Park SA, L.P., a Texas limited partnership ("Lessor"), and
     American TeleSource International, Inc., a Texas corporation ("Lessee").

     1.02  Leased Premises. In consideration of the rents, terms, provisions and
covenants of this Lease, Lessor hereby leases, lets and demises to the Lessee
the following described premises ("Leased Premises"): The area shown on the
attached Exhibit "A" consisting of approximately 26,250 rentable square feet at
the western end of the building to be constructed and called University Park
Tech Center II in San Antonio, Texas 78249, which consists of 84,525 square
feet, and which is located on the land shown on Exhibit "B" attached hereto and
                                                -----------
incorporated herein for all purposes.

Lessor and Lessee agree that final square footage for the purpose of rent
calculations will be determined by Lessee's architect, using then-current BOMA
standards (except that the space shall be measured from the edge of the roof for
the exterior space adjacent to the exterior doorways) based on Lessee
Improvements Final Plans and Specifications, subject to Lessor's approval, which
may not be unreasonably refused or delayed.

     1.03  Term.  Subject to and upon the conditions set forth herein, the term
(the "Term") of this Lease commences on December 15, 1999 (the "Commencement
Date") and terminates one hundred and two (102) months thereafter (the
"Termination Date").  Except as provided in Addendum 1 attached hereto and
                                            ----------
incorporated herein for all purposes, Lessee agrees that Lessor will not be
liable to Lessee if Lessor does not deliver possession of the Leased Premises to
Lessee on the Commencement Date, and Lessor's non-delivery of the Leased
Premises to Lessee on the Commencement Date will not change the terms of this
Lease or the obligations of Lessee hereunder. If delivery of the Leased Premises
is delayed for any reason other than Lessee Delay (as hereinafter defined),
Lessor and Lessee agree that the Commencement Date will be delayed until
Substantial Completion (as hereinafter defined) of the Leased Premises, in which
event the Term will be automatically extended for a period of time equal to the
delay in Substantial Completion of the Leased Premises. If the Commencement Date
is delayed, Lessor and Lessee shall, upon such delivery, execute an amendment to
this Lease setting forth the actual Commencement Date and Termination Date. If
Lessee enters the Leased Premises prior to Substantial Completion, Lessee shall
execute and deliver to Lessor an Early Occupancy Agreement in a reasonable form
provided by Lessor whereby Lessee releases Lessor from all liabilities, claims
and causes of action arising out of any construction or other work performed at
the Leased Premises and agrees to pay utility charges incurred by Lessee during
such early occupancy. If the Termination Date falls on a day other than the last
day of a month, the parties agree that the Term is automatically extended by the
number of days necessary to cause the Term to end on the last day of a month.

     1.04  Base Rent, Security Deposit. Base Rent is $25,987.50 net per month
based upon an assumed 26,250 rentable square footage in the Leased Premises and
shall be adjusted by $11.88 per rentable square foot per year based on the
recalculation under Section 1.02 above. Security Deposit is $ 12,993.75.

     1.05 Addresses.
<PAGE>

     Lessor's Address:                       Lessee's Address:

     ACLP University Park SA, L.P.           American TeleSource International,
     17400 Dallas Parkway                    Inc.
     Suite 216                               12500 Network Blvd.
     Dallas, Texas 75287                     Suite 407
     FAX (972) 407-9068                      San Antonio, Texas 78249
     FAX (210) 558-6095

     With a copy to:
     CMC Commercial Realty Group, Inc.
     5400 LBJ Freeway
     Suite 1450
     Dallas, Texas 75240
     FAX (972) 770-2805

     1.06  Permitted Use. The Leased Premises may be used for office space and
operation of telecommunications equipment.

     1.07  Leasing Term Limitation on Adjacent Space and Right of First Refusal.
Lessor agrees that Lessee may lease the First Bay shown on Exhibit "A" or the
Second Bay shown on Exhibit "A" at any time prior to Lessor leasing the First
Bay or the Second Bay to another person. Lessor agrees that it will notify
Lessee at least thirty (30) days prior to entering into a lease of the First Bay
or Second Bay, and will not enter into a lease for the First Bay for a term that
continues longer than thirty-six (36) months or the Second Bay for a term that
continues longer than sixty (60) months. Lessor further agrees that it will
notify Lessee ninety (90) days prior to the expiration of any lease of the First
Bay or Second Bay (or immediately upon learning that the First Bay or Second Bay
are to become available prior to the expiration of their respective lease) and
Lessee will have fifteen (15) days following receipt of notice to notify Lessor
that it elects to lease the First Bay or Second Bay. If Lessee does not notify
Lessor that it elects to lease the First Bay or Second Bay within fifteen (15)
days, Lessor may re-let the First Bay or Second Bay for a term of up to thirty-
six (36) months and the Second Bay for a term of up to sixty (60) months. If
Lessee elects to lease the First Bay or Second Bay pursuant to this Section,
then Lessor and Lessee will execute a modification of this Lease such that the
First Bay or Second Bay become part of the Leased Premises and are leased on the
same terms and conditions as provided in this Lease for the initial Leased
Premises, including renewal options, but not including the rental per square
foot, finish out allowance, and refurbishment allowance, with an additional
security deposit to be calculated in the same manner as the security deposit for
the Leased Premises, and with the term of the lease for the First Bay or Second
Bay to expire on the Termination Date. If Lessee elects to lease the First Bay
or Second Bay prior to the time that Lessor completes the Lessee Improvements,
then the First Bay and Second Bay will be leased on all of the same terms and
conditions as the initial Leased Premises, including rental per square foot,
renewal options, finish out allowance, and refurbishment allowance. The date for
completion of Lessee Improvements in the First Bay or Second Bay will be
established consistently with the time frames for completion of Lessee
Improvements for the initial Leased Premises.

     1.08  Lessee's Future Expansion Needs. Lessor acknowledges that Lessee
expects its business to grow significantly and that Lessee may require space in
addition to the Leased Premises, First Bay and Second Bay. Lessor will keep
Lessee informed of the status of the remaining space in the Building and give
Lessee a reasonable opportunity to lease additional space that becomes available
on reasonable terms and conditions.

     1.09  Renewal Terms. Lessor agrees that Lessee may renew the Lease for two
successive sixty (60) month renewal terms (each a "Renewal Term") by giving
Lessor written notice of renewal at least one hundred eighty (180) days prior to
the expiration of the Term or the first Renewal Term, respectively. The Lease
will continue on the same terms and conditions during any Renewal Term, except
that the rental rate per square foot shall be adjusted to ninety five percent
(95%) of the prevailing market rate for comparable buildings in San Antonio at
the time of renewal (taking into consideration the age and quality of the
structure, type of building, location of the space in the building, definition
of the leased area, estimated lease-up time, credit standing and financial
status of the Lessee, term, extent of services provided by landlord, brokerage
fees, leasehold improvement allowances, moving allowances, rental abatements and
other incentive being offered). If there is a difference in opinion between
Lessor and Lessee regarding the prevailing market rate of rental at the time of
Renewal, Lessor and Lessee will negotiate in
<PAGE>

good faith to resolve the difference. Lessor and Lessee will also negotiate in
good faith to establish a refurbishment allowance for the Leased Premises, which
shall be administered by Lessor on the same terms and conditions as the
Improvement Allowance for the Initial Lessee Improvements. Lessee may withdraw
its notice of renewal if agreement on the prevailing market rate of rental is
not reached within sixty (60) days of the beginning of the proposed Renewal
Term.

     1.10  Contingencies. Lessor agrees that if by May 1, 1999, Lessor has
           failed to acquire title to the land on which the Building is to be
           constructed, or if by June 1, 1999 it has not commenced construction
           of the Building, Lessee may terminate this Lease on one (1) day's
           advance written notice. Lessor agrees that Lessee's security deposit
           and seventh months' rent is due upon execution of the Lease; however
           Lessor and Lessee further agree that such payment will not be
           deposited until such time as Lessor has acquired title to the land on
           which the Building is to be constructed.

ARTICLE 2.00 - RENT

     2.01  Base Rent. Lessee agrees to pay monthly as base rent during the term
of this Lease without notice, demand, counter-claim, set-off or abatement,
except as otherwise set forth herein, the sum of money set forth in Section 1.04
of this Lease, which amount is payable to Lessor at the address shown above,
except that Lessee shall not pay any base rent for the first six full calendar
months following the Commencement Date. One monthly installment of rent is due
and payable on the date of execution of this Lease by Lessee for the seventh
month's rent and a like monthly installment is due and payable on or before the
first day of each succeeding calendar month during the term of this Lease;
provided, if the Commencement Date should be a date other than the first day of
a calendar month, the free rental period set forth above will begin on the
Commencement Date and the rental for the remainder of the calendar month in
which the free rental period ends will be prorated and will due on the first day
of the calendar month first following the end of the free rental period. Lessee
shall pay, as additional rent, all other sums due under this Lease.

     2.02  Additional Rent. Lessee agrees to pay as additional rent, without
deduction or set-off of any kind except as otherwise set forth herein, Lessee's
pro rata share of all ad valorem taxes and installments of special assessments
(including dues and assessments by means of deed restrictions and/or owner's
associations) lawfully levied or assessed against the Building (as hereinafter
defined) of which the Leased Premises are a part and any and all insurance
required herein or which is standard for similar projects (specifically
including fire and casualty, commercial general liability and rent loss
insurance). Said ad valorem taxes, assessments and insurance shall be prorated
and paid on or before the first day of every month commencing on the
Commencement Date, in advance, as additional rent. The proration shall be based
upon Lessor's estimate of ad valorem taxes, assessments and insurance for the
current calendar year, provided, that in the event Lessor is required under a
mortgage, deed of trust, underlying lease or loan agreement covering the
Building to escrow ad valorem taxes, assessments or insurance, Lessor may but
shall not be obligated, to use the amount required to be escrowed as a basis for
its estimate. There will be an annual accounting as to actual ad valorem taxes,
assessments and insurance and appropriate payment or credits made. To the extent
the Commencement Date or Termination Date of the Lease is not on the first day
of the calendar year or last day of the calendar year respectively, Lessee's
liability for ad valorem taxes, assessments and insurance shall be subject to a
pro rata adjustment based on the number of days of any such year during which
the Term is in effect. Lessee shall have the right at its expense to contest or
appeal by appropriate proceedings any value assessment rendered by applicable
taxing authorities and Lessor shall cooperate to the extent reasonably necessary
in such contest or appeal. To the extent the Leased Premises are part of a
multi-occupancy building, Lessee shall pay a pro rata share of such ad valorem
taxes, assessments and insurance, such pro rata share to be equal to the product
obtained by multiplying the total of such real property taxes assessments and
insurance by a fraction, the numerator of which shall be the number of square
feet of floor area of the Leased Premises and the denominator of which shall be
the number of square feet of floor area in the Building of which the Leased
Premises are a part.

     2.03  Operating Expenses. Lessee agrees to pay, as additional rent,
Lessee's pro rata share (as determined by the formula set forth in Section 2.02
above) of Lessor's Operating Expenses for the Building without deduction or set-
off of any kind except as otherwise set forth herein. Lessor may invoice Lessee
monthly for Lessee's pro rata share of the estimated Operating Expenses for each
calendar year, which amount shall be adjusted from time-to-time based upon
anticipated Operating Expenses. As of the date hereof, it is estimated that the
Operating Expenses, taxes and insurance for calendar year 2000 will be
<PAGE>

approximately $2.20 per rentable square foot. Lessor agrees that the Lessee's
portion of the Operating Expenses for common area maintenance, less costs of
utilities, costs required to meet applicable laws, and capitalized costs of
capital improvements and operating efficiency devices, will not exceed seventy-
eight cents ($.78) per rentable square foot during the first year of the Term
(the "Base Amount"), and will not increase for any year by more than five
percent (5%) per year (cumulative) over the Base Amount. Within four months
following the close of each calendar year, Lessor shall provide Lessee an
accounting showing in reasonable detail all computations of additional rent due
under this Section. In the event the accounting shows that the total of the
monthly payments made by Lessee exceeds the amount of additional rent due by
Lessee under this Section, such amount shall be credited against the next
required payment of base rent. In the event the accounting shows that the total
of the monthly payments made by Lessee is less than the amount of additional
rent due by Lessee under this Section, the account shall be accompanied by an
invoice for the additional rent. If this Lease shall terminate on a day other
than the last day of a calendar year, the amount of any additional rent payable
by Lessee applicable to the year in which such termination shall occur shall be
prorated on the ratio that the number of days from the commencement of the
calendar year to and including the termination date bears to 365. Provided
Lessee is not in default of any terms of this Lease, Lessee shall have the
right, at its own expense, to audit Lessor's books relevant to the additional
rent payable under this Section. With respect to such audit, Lessee 1) may
review Lessor's books during office hours, 2) must perform such audit at the
location of Lessor's books, 3) must request such audit within six (6) months of
receipt of its annual reconciliation of Operating Expenses, 4) must deliver to
Lessor a copy of the results of such audit, 5) may not audit the same calendar
year more than one time. If, as a result of such audit, it is determined that
the Operating Expenses have been overstated by 3% or more, Lessor shall be
required to reimburse Lessee for the costs of such audit. Assignees of Lessee
may only audit periods for which they occupy the Leased Premises and subtenants
of Lessee shall have no audit rights. Lessee agrees to pay any additional rent
due under this Section within ten (10) days following receipt of the invoice or
accounting showing additional rent due.

     2.04  Definition of Operating Expenses. The term "Operating Expenses"
includes all expenses incurred by Lessor with respect to the maintenance and
operation of the Building (except for items described below) and includes, but
is not limited to, the following: maintenance, repair and replacement costs;
security; wages and benefits payable to employees of Lessor to the extent their
duties are directly connected with the operation and maintenance of the
Building; management fees, all services, utilities for common areas, supplies,
repairs, replacement or other expenses for maintaining and operating the common
parking and plaza areas; the cost, amortized over its useful life, of any
expense required to be capitalized under GAAP principles other than capital
improvements; the cost, amortized over its useful life, of any capital
improvement made to the Building by Lessor after the date of this Lease, if
required under any governmental law or regulation other than improvements made
to the Building to effect compliance with the Americans With Disabilities Act
(the "ADA") or as otherwise set forth herein, which capital improvements must be
of mutual benefit to all tenants of the Building; and the cost, amortized over
its useful life, of installation of any device or other equipment to the extent
it improves the operating efficiency of any system within the Leased Premises
and thereby reduces Operating Expenses, provided that, prior to installing any
such device or equipment, Lessor will inform Lessee of such installation and the
estimated cost savings and Lessor and Lessee must reasonably agree upon the
estimated cost savings before agreeing to such installation. The term Operating
Expenses does not include the following: expenses incurred to maintain the roof,
foundation and structural soundness of the exterior walls of the Building;
expenses incurred should the entire roof the Building need to be replaced;
expenses to bring the Building into compliance with applicable law such as the
ADA and Environmental Laws, expenses incurred to abate or remove any Hazardous
Substance in the Building that was placed there by Lessor, income and franchise
taxes of Lessor; expenses incurred in leasing to or procuring of lessees,
leasing commissions, advertising expenses and expenses for the renovating of
space for new lessees; interest or principal payments on any mortgage or other
indebtedness of lessor; compensation paid to any employee of Lessor other than
maintenance and property management personnel to the extent these services are
directly associated with the operation and maintenance of the Building; any
depreciation allowance or expense (except for depreciation of capital
improvements and equipment specifically included within the definition of
Operating Expenses); or operating expenses which are the responsibility of
Lessee or any other lessee of the Building; or expenses (herein called "Defect
Expenses") incurred as a result of or caused by latent defects, punch list
items, or Lessor's failure to construct the Shell Building Improvements or
Lessee Improvements in accordance with the requirements of this Lease and
substantially in accordance with the Final Shell Plans and Specifications and
Lessee Improvements Final Plans and Specifications as provided herein (such
items being herein called "Defects"); and/or operating expenses otherwise caused
by or resulting from Lessor's breach of its obligations under the Lease.
<PAGE>

     2.05  Late Payment Charge. Other remedies for nonpayment of rent
notwithstanding, if the monthly rental payment is not received by Lessor on or
before the fifth day of the month for which the rent is due, or if any other
payment due Lessor by Lessee is not received by Lessor on or before the fifth
day of the month next following the month in which Lessee was invoiced, Lessee
agrees to pay a late payment charge of five percent (5%) of such past due amount
in addition to such amounts owed under this Lease, provided, however, that
Lessee is hereby granted a waiver of this late payment charge once every twelve
(12) months during the term of this Lease. In addition, Lessor is entitled to
charge one-hundred dollars ($100.00) for each check or payment which is not
honored by Lessee's bank. Said charge is in addition to any other amounts owed
under this Lease.

     2.06  Security Deposit. The security deposit set forth above will be held
by Lessor for the performance of Lessee's covenants and obligations under this
Lease, it being expressly understood that the deposit is not an advance payment
of rental or a measure of Lessor's damage in case of default by Lessee. Upon the
occurrence of any event of default by Lessee or breach by Lessee of Lessee's
covenants under this Lease, Lessor may, from time to time, without prejudice to
any other remedy, use the security deposit to the extent necessary to make good
any arrears of rent, or to repair any damage or injury, or pay any expense or
liability incurred by Lessor as a result of the event of default or breach of
covenant, and any remaining balance of the security deposit will be returned by
Lessor to Lessee within a reasonable period of time following termination of
this Lease. If any portion of the security deposit is so used or applied, Lessee
shall upon ten days written notice from Lessor, deposit with Lessor by cash or
cashier's check an amount sufficient to restore the security deposit to its
original amount.

     2.07  Holding Over. In no event may Lessee remain in the Leased Premises
following the expiration or termination of this Lease without Lessor's prior
written consent. If Lessee does not vacate the Leased Premises upon the
expiration or termination of this Lease, Lessee agrees that it will be a tenant
at will for the holdover period and that all of the terms and provisions of this
Lease are applicable during that period, except that Lessee shall pay Lessor as
base rental for the period of such holdover an amount equal to 1.50 times the
base rent being paid by Lessee immediately prior to the expiration or
termination of the Lease. Lessee agrees to vacate and deliver the Leased
Premises to Lessor immediately upon Lessee's receipt of notice from Lessor to
vacate. Such notice may be given pursuant to the notice provisions of Section
14.07 herein. Lessee agrees to pay the rental payable during the holdover period
to Lessor on demand. No holding over by Lessee, whether with or without the
consent of Lessor and notwithstanding receipt by Lessee of an invoice from
Lessor for holdover rent, will extend the term of this Lease. Additionally,
Lessee shall pay to Lessor all damages sustained by Lessor as a result of such
holding over by Lessee.

                       ARTICLE 3.00 - OCCUPANCY AND USE

     3.01  Use. Lessee warrants and represents to Lessor that the Leased
Premises may be used and occupied only for the purpose as set forth in Section
1.06. Lessee shall occupy the Leased Premises, conduct its business and control
its agents, employees, invitees and visitors in such a manner as is lawful,
reputable, will not create a nuisance, interfere with standard Building
operations, or affect the structural integrity or design capabilities of the
Building. Lessee shall not permit any operation which emits any odor or matter
which intrudes outside the Leased Premises, attracts rodents, use any apparatus
or machine which makes undue noise or causes vibration in any portion of the
Building or otherwise interfere with, annoy or disturb any other party outside
the Leased Premises, including without limitation, any other tenant in the
Building. Lessee shall neither permit any waste on the Leased Premises nor allow
the Leased Premises to be used in any way which would, in the reasonable opinion
of Lessor, be extra hazardous on account of fire or which would in any way
increase or render void the fire insurance on the Building. If at any time
during the Term the State Board of Insurance or other insurance authority
disallows any of Lessor's sprinkler credits or imposes an additional penalty or
surcharge in Lessor's insurance premiums because of Lessee's original or
subsequent placement or use of storage racks or bins, method of storage or
nature of Lessee's inventory or any other act of Lessee, Lessee agrees to pay as
additional rent the increase in Lessor's insurance premiums. Notwithstanding
anything set forth in this Section 3.01, in no way does Lessor warrant or
represent, either expressly or impliedly, that Lessee's use of the Leased
Premises is in accordance with applicable codes or ordinances of the
municipality within which the Building is located. Lessee agrees to indemnify
and hold Lessor harmless from all claims, demands, actions, liabilities, costs,
expenses, damages and obligations of any nature arising from or as a result of
the use of the Leased Premises by Lessee in violation of applicable codes or
ordinances of the municipalities or any other government bodies within which the
building is located. The foregoing indemnification and the responsibilities of
Lessee survive the termination or expiration of this Lease.
<PAGE>

     3.02  Signs. No sign of any type or description may be erected, placed or
painted in or about the Leased Premises of Building, including those advertising
the Leased Premises for sublease, except (i) those signs which are in
conformance with Lessor's sign criteria attached as Exhibit "C" and, (ii) at
                                                    -----------
Lessee's option and expense, a free-standing "monument" sign consistent in
quality and appearance with the architectural standards of the Building, and as
approved in advance by Lessor. All signs must be in conformance with applicable
governmental requirements and limitations (including any applicable restrictive
covenants). Such permitted signs must be removed by Lessee upon expiration or
termination of the Lease at Lessee's sole cost and expense. Any damage or
discoloration from such removal will be repaired at Lessee's sole cost and
expense.

     3.03  Compliance with Laws, Rules and Regulations. Lessee, at Lessee's sole
cost and expense (except as provided in Section 2.04 hereof), shall comply with
all laws, ordinances, orders, rules and regulations now in effect or enacted
subsequent to the date hereof by state, federal, municipal or other agencies or
bodies having jurisdiction over Lessee or the use, condition and occupancy of
the Leased Premises except that Lessor shall be responsible for construction of
the Lessee Improvements in compliance therewith as of the Commencement Date,
including, but not limited to, compliance with the ADA as to the Building, but
excluding the interior of the Leased Premises which is Lessee's responsibility.
Lessee will comply with the rules and regulations of the Building adopted by
Lessor which are set forth on a schedule attached to this Lease. At any time,
Lessor may change and amend the rules and regulations in any reasonable manner
not inconsistent with the terms of this Lease as may be deemed advisable for the
safety, care, cleanliness, preservation of good order and operation or use of
the Building or the Leased Premises. All changes and amendments to the rules and
regulations of the Building will be sent by Lessor to Lessee in writing and must
thereafter be carried out and observed by Lessee.

     3.04  Warranty of Possession and Enjoyment. Lessor warrants that it has the
right and authority to execute this Lease, and Lessee, upon payment of the
required rents and subject to the terms, conditions, covenants and agreements
contained in this Lease, is entitled to possession and quiet enjoyment of the
Leased Premises during the full term of this Lease as well as any extension or
renewal thereof. Lessor is not responsible for the acts or omissions of any
other lessee or third party that may interfere with Lessee's use and enjoyment
of the Leased Premises.

     3.05  Inspection. Lessor or its authorized agents may at any and all
reasonable times enter the Leased Premises to inspect the same, conduct tests,
environmental audits or other procedures to determine Lessee's compliance with
the terms hereof; to supply any other service to be provided by Lessor; to show
the Leased Premises to prospective purchasers, lessees, (within six months prior
to termination of this Lease), or mortgagees; to alter, improve or repair the
Leased Premises or any other portion of the Building or for any other purpose
Lessor deems reasonably necessary. LESSEE HEREBY WAIVES ANY CLAIM FOR DAMAGES
FOR INJURY OR INCONVENIENCE TO OR INTERFERENCE WITH LESSEE'S BUSINESS, ANY LOSS
OF OCCUPANCY OR USE OF THE LEASED PREMISES, AND ANY OTHER LOSS OCCASIONED BY
INSPECTIONS MADE UNDER THIS SECTION INCLUDING CLAIMS RESULTING FROM THE
NEGLIGENCE OF LESSOR BUT EXCLUDING ANY CLAIMS RESULTING FROM THE GROSS
NEGLIGENCE OR WILLFUL MISCONDUCT OF LESSOR. Lessee shall not change Lessor's
lock system or in any other manner prohibit Lessor from entering the Leased
Premises. Lessor is entitled to use any and all means which Lessor may deem
proper to open any door in an emergency without liability therefor. During the
final one-hundred eighty days of the Lease term, Lessor or its authorized agents
have the right to erect or maintain on or about the Leased Premises or the
Building customary signs advertising the Leased Premises for lease or sale.

     3.06  Hazardous Waste. The term "Hazardous Substances," as used in this
Lease means pollutants, contaminants, toxic or hazardous wastes, or any other
substances, the use and/or the removal of which is required or the use of which
is regulated, restricted, prohibited or penalized by any "Environmental Law,"
which term means any federal, state or local law, ordinance or other statute of
a governmental or quasi-governmental authority relating to pollution or
protection of the environment. Lessee hereby agrees that (i) no activity will be
conducted on the Leased Premises that will produce any Hazardous Substance,
except for such activities that are part of the ordinary course of Lessee's
business activities (the "Permitted Activities"), provided said Permitted
Activities are conducted in accordance with all Environmental Laws and have been
approved in advance in writing by Lessor; Lessee shall obtain all required
permits and pay all fees and conduct any testing required by any governmental
agency; (ii) the Leased Premises will not be used in any manner for the storage
of any Hazardous Substances except for the temporary storage of such materials
that are used in the ordinary course of Lessee's business (the "Permitted
Materials") provided such Permitted Materials are properly stored in a manner
and location meeting all
<PAGE>

Environmental Laws and approved in advance in writing by Lessor; Lessee shall
obtain all required permits and pay all fees and conduct any testing required by
any governmental agency in connection with the Permitted Materials; (iii) no
portion of the Leased Premises or Building will be used as a landfill or a dump;
(iv) Lessee will not install any underground or above ground tanks of any type;
(v) Lessee will not allow any surface or subsurface conditions to exist or come
into existence that constitute, or with the passage of time may constitute a
public or private nuisance; (vi) Lessee will not permit any Hazardous Substances
to be brought onto the Leased Premises or Building, except for the Permitted
Materials, and if so brought or found located thereon (except for pre-existing
conditions or matters caused by the Lessor), the same must be immediately
removed, with proper disposal, and all required cleanup procedures must be
diligently undertaken pursuant to all Environmental Laws. Lessor or Lessor's
representative's may, but are not required to, enter the Leased Premises for the
purpose of inspecting the storage, use and disposal of Permitted Materials to
ensure compliance with all Environmental Laws. Should it be determined, in
Lessor's sole opinion, that said Permitted Materials are being improperly
stored, used, or disposed of, then Lessee shall immediately take such corrective
action as requested by Lessor. Should Lessee fail to take such corrective action
within twenty-four (24) hours, Lessor has the right to perform such work and
Lessee shall promptly reimburse Lessor for any and all costs associated with
said work. If at any time during or after the term of the Lease, the Leased
Premises or Building are found to be so contaminated or subject to said
conditions as a result of Lessees breach of the terms of this Lease, Lessee
shall diligently institute proper and thorough cleanup procedures at Lessee's
sole cost. Before taking any action to comply with Environmental Laws or to
clean up Hazardous Substances contaminating the Leased Premises or Building,
Lessee shall submit to Lessor a plan of action, including any and all plans and
documents required by any Environmental Law to be submitted to a governmental
authority (collectively a "plan of action"). Such plan of action must be
implemented by a licensed environmental contractor. Before Lessee begins the
actions necessary to comply with Environmental Laws or to clean up contamination
from Hazardous Substances, Lessor must have (1) approved the nature, scope and
timing of the plan of action, and (2) approved any and all covenants and
agreements to effect the plan of action. Lessee agrees to indemnify and hold
Lessor harmless from all claims, demands, actions, liabilities, costs, expenses,
damages and obligations of any nature arising from or as a result of the use of
the Leased Premises or Building by Lessee in violation of this Section 3.06 but
excluding pre-existing conditions or matters resulting from the negligence or
willful misconduct of Lessor. The foregoing indemnification and the
responsibilities of Lessee survive the termination or expiration of this Lease.

     Lessee represents that it has not been previously cited for any
environmental violations by any applicable governmental agency and that there
are no Permitted Materials to be stored in or upon the Leased Premises.  In no
event will any Permitted Materials be stored in or upon the Leased Premises
without Lessor's prior written consent.

     3.07  Parking and Road Use. Except as the number of spaces may be reduced
pursuant to Section 3.08, Lessor will ensure that Lessee will have available to
use, for the benefit of Lessee, its employees, customers, invitees and
licensees, six (6) parking spaces for each 1000 rentable square feet of Leased
Premises in the parking areas adjacent to the Building of which the Leased
Premises are a part on an unassigned, unreserved basis, subject to reasonable
regulation by Lessor. Lessor may use additional parking spaces if available, on
a first come, first serve basis unless such use interferes with another tenant's
rights. Lessor reserves the right in its sole discretion to designate specific
areas within the parking areas for the exclusive use of visitors and invitees to
the Building and others. Included in the aggregate allowance of parking spaces
shall be fifteen (15) designated, reserve parking spaces for the exclusive use
of Lessee, location of such spaces to be agreed upon by Lessor and Lessee and to
be shown on the site plan attached hereto as Exhibit "A", provided that Lessor
shall not be responsible for monitoring use of such spaces. Should Lessee
increase the square footage of the Leased Premises at any time, Lessee shall be
allowed additional parking spaces according to the ratio set forth herein. Any
parking permitted by Lessor on any common drive areas by Lessee or any of
Lessee's employees, customers, invitees or licensees will be permitted upon the
express condition that all such drives must be kept clear for through traffic of
all vehicles, including tractor-trailers. No driving or parking of any vehicles
on non-paved areas adjoining the Building or within the Project of which the
Building is a part is permitted. Lessee's failure to use all of the parking
spaces allocated to it under this Section will not constitute a waiver by Lessee
of the right to use those parking spaces at a later time.

     3.08  Satellite Dishes. Lessor agrees that Lessee may locate up to three
(3) satellite dishes in the rear parking lot (i.e., southern side of the
Building), provided that each dish may not exceed thirty feet in diameter and
thirty feet in height. Lessor agrees that Lessee may locate the dishes in any
portion of the rear parking lot in a fenced area, said fence to be provided and
maintained at the sole cost and expense of Lessee, not to exceed thirty five
feet by two hundred feet, but that the number of parking spaces available to
Lessee pursuant to Section 3.07 will
<PAGE>

be reduced by the actual number of parking spaces eliminated by the placement of
the dishes on the location shown on Exhibit "A", provided that no satellite dish
exceeds 30 feet in diameter and 30 feet in height.

                  ARTICLE 4.00 - UTILITIES, SERVICE, SIGNAGE

     4.01  Security Lighting. Lessor shall install security lighting at all
entrances to the Leased Premises and in the parking lots adjacent to the Leased
Premises at its expense; provided, however, the Lessor shall make no
representation or warranty as to the sufficiency or adequacy of such lighting or
the effectiveness thereof for security.

     4.02  Building Services. Lessor shall provide the normal utility service
connections to the Building. Lessee shall pay directly to the appropriate
supplier the cost of all utility services to the Leased Premises, including, but
not limited to, any required security deposits and initial connection charge,
all charges for gas, electricity, telephone, water, sanitary and storm sewer
service and security systems. If any services are jointly metered with other
Leased Premises or property (for example, exterior lighting), Lessor shall make
a reasonable determination of Lessee's proportionate share of the cost of such
services and Lessee shall pay such share to Lessor within ten (10) days of
receipt of any invoice thereof. Lessee shall pay all costs caused by Lessee
introducing excessive pollutants or solids other than ordinary human waste into
the sanitary sewer system, including permits, fees and charges levied by any
governmental subdivision for any such pollutants or solids. Lessee shall be
responsible for the installation and maintenance of any dilution tanks, holding
tanks, settling tanks, sewer sampling devices, sand traps, grease traps or
similar devices as may be required by any governmental subdivision for Lessee's
use of the sanitary sewer system. If the Leased Premises are in a multi-
occupancy Building, Lessee shall pay all surcharges levied due to Lessee's use
of sanitary sewer or waste removal services insofar as such surcharges affect
Lessor or other Lessees in the Building. Except as set forth herein, Lessor
shall not be required to pay for any utility service, supplies or upkeep in
connection with the Leased Premises or Building. Utility services for the common
areas shall be part of Operating Expenses.

     Lessee agrees that Lessor is not liable to Lessee in any respect for
damages to either person, property or business on account of any interruption or
failure of utilities or services furnished by Lessor provided that Lessor uses
reasonable diligence to repair the same promptly. No such interruption or
failure may be construed as an eviction of Lessee or entitle Lessee to (i) any
abatement of rent, (ii) terminate the Lease, or (iii) be relieved from
fulfilling any covenant or agreement contained herein. Should any malfunction of
the improvements or facilities to the Leased Premises or Building (which by
definition do not include any improvements or facilities of Lessee above
Building standard improvements) occur for any reason, Lessor shall use
reasonable diligence to repair same promptly, but Lessee will not be entitled to
any claim for rebate or abatement of rent or damages on account of such
malfunction or of any interruptions in service occasioned thereby or resulting
therefrom.

     4.03  Theft or Burglary. Lessee expressly acknowledges that whether or not
Lessor, from time to time, elects to provide security services, Lessor has not,
nor will Lessor be deemed to have, warranted the efficiency of any security
personnel, service, procedures or equipment and Lessor is not liable in any
manner for the failure of any of the foregoing to prevent or control or
apprehend anyone suspected of theft, personal injury, property damage or any
criminal conduct in, on or around the Building. Lessee agrees that Lessor is not
liable to Lessee for losses to Lessee's property or personal injury caused by
criminal acts or entry by unauthorized persons into the Leased Premises. Lessee
is responsible for the cost of repairs of damage and restoration of the Leased
Premises following any such act.

                     ARTICLE 5.00 - REPAIRS AND MAINTENANCE

     5.01  Existing Conditions. On the Commencement Date, Lessee shall be deemed
to have accepted the Leased Premises in their then existing condition, subject
to all recorded matters, laws, ordinances, and governmental regulations and
orders.; provided that, Lessee's acceptance of the Leased Premises shall not
relieve Lessor from any maintenance and repair obligations under this Lease.
Lessee acknowledges that neither Lessor nor any agent of Lessor has made any
warranty or representation of any kind, either express or implied as to the
condition of the Leased Premises or the suitability of the Leased Premises for
Lessee's intended use other than that the Leased Premises will be constructed in
accordance with the Lessee Improvements Final Plans and Specifications and will
be free from Hazardous Materials. The taking of the possession of the Leased
Premises by Lessee is intended by the
<PAGE>

parties to be conclusive evidence that Lessee accepts the Leased Premises and
Lessor has complied with its obligations of Section 6.01 herein except for
Defects (as defined in Section 2.04 hereof), the presence of Hazardous
Materials, and punch list items. Prior to taking occupancy of the Leased
Premises, Lessee shall sign a copy of the space plan of the Leased Premises
acknowledging its condition on the date thereof (unless Lessor waives such
requirement) and execute the Certificate of Acceptance form attached as Exhibit
"D" accepting such condition of the Premises except for Defects, the presence of
Hazardous Materials and punch list items.

     5.02  Lessor Repairs And Maintenance. Lessor shall manage the Building in
accordance with property management standards customary to the area and will
keep the Building in compliance with all legal and regulatory requirements
(including Environmental Laws, Americans with Disabilities Act, and municipal
codes and ordinances). Lessor agrees to indemnify and hold Lessee harmless from
all claims, demands, actions, liabilities, costs, expenses, damages and
obligations of any nature arising from or as a result of the failure of the
building to be in compliance with applicable laws and regulation. Lessor is not
required to make any improvements, replacements or repairs of any kind or
character to the Leased Premises during the Term. Lessor shall maintain the
roof, foundation and structural soundness of exterior walls of the Building,
mechanical, electrical and plumbing systems serving the Building and common
areas, in good repair and condition except for reasonable wear and tear. Lessor
shall also perform all ground maintenance, landscaping, pest control, and
removal of debris from outside receptacles. Lessee agrees that Lessor is not
liable to Lessee, except as expressly provided in this Lease, for any damage or
inconvenience, and Lessee is not entitled to any abatement or reduction of rent
by reason of any repairs, reasonable alterations or additions made by Lessor
under this Lease. Should Lessor not repair or maintain the Building or the
Leased Premises as required hereunder, after providing written notice to Lessor
and after a thirty (30) day opportunity to cure by Lessor, or such longer period
as shall be necessary, provided that Lessor has not commenced such repair within
such 30 day period and has not diligently pursued same thereafter, Lessee may
make such repairs or perform such maintenance and Lessor shall promptly
reimburse Lessee for any reasonable expenses incurred by Lessee in performing
such work, or if the Leased Premises are untenantable, Lessee may terminate this
Lease.

     5.03  Lessee Repairs And Maintenance. Lessee shall, at its sole cost and
expense, maintain and repair the Leased Premises in good repair and condition,
including, but not limited to carpet or other floor covering, interior
partitions, doors, interior side of demising walls, telephone and computer
cabling that serves Lessee's equipment exclusively, any supplemental air
conditioning, interior water closets, kitchens and plumbing in connection
therewith and any alterations, additions or improvements made by or on behalf of
Lessee. Lessee shall take good care of all personal property and fixtures
located within the Leased Premises. Lessee shall repair and pay for any damage
caused by any act or omission of Lessee or Lessee's agents, employees, invitees,
licensees or visitors to the Leased Premises, the Building, or the project. If
Lessee fails to maintain, repair or replace promptly as required herein, Lessor
may, at its option, and following at least thirty (30) days' advance written
notice to Lessee, perform on Lessee's behalf and charge the cost of such
performance to Lessee as additional rent which is due and payable by Lessee
within ten (10) days from receipt of Lessor's invoice. Costs incurred under this
section are the total responsibility of Lessee.

     5.04  Request for Repairs. All requests for repairs or maintenance that are
the responsibility of Lessor pursuant to any provision of this Lease must be
made in writing to Lessor at the address in Section 1.05 and delivered pursuant
to Section 14.07. After receipt of written notice, Lessor is entitled to a
reasonable time within which to perform such repairs or maintenance.

     5.05  Lessee Damages. Lessee shall not allow any damage to be committed on
any portion of the Leased Premises or Building, and at the termination of this
Lease, by lapse of time or otherwise, Lessee shall deliver the Leased Premises
to Lessor in as good condition as existed at the Commencement Date of this
Lease, ordinary wear and tear and casualty loss excepted. Lessor's standard
move-out checklist will be followed by Lessee to ensure compliance with this
provision. The cost and expense of any repairs necessary to restore the
condition of the Leased Premises must be borne by Lessee. Should Lessor be
required to expend any sums to ensure compliance with this Section 5.05, Lessee
shall reimburse Lessor within ten (10) days of receipt of notice from Lessor.

     5.06  Maintenance Contract. Lessor may, as an Operating Expenses, during
the term of this Lease maintain a regularly scheduled preventative
maintenance/service contract on an annual basis with a maintenance contractor
for the servicing of all general sprinkler systems, hot water, heating and air
conditioning systems and equipment within or servicing the Building. Lessee
shall maintain, at Lessee's sole cost and expense, a regularly
<PAGE>

scheduled preventative maintenance/service contract on an annual basis with a
maintenance contractor for the servicing of all hot water, heating and air
conditioning systems within or exclusively servicing the Leased Premises.

                  ARTICLE 6.00 - ALTERATIONS AND IMPROVEMENTS

     6.01 Initial Lessee Improvements.

             A.  Lessee Improvements. Lessee shall prepare final plans and
                 -------------------
             specifications for construction of the Lessee Improvements desired
             by Lessee and shall deliver to Lessor by July 1, 1999, two (2)
             copies of such plans and specifications and the names of two
             proposed contractors to construct the Lessee Improvements for
             Lessor approval. Lessor will promptly either approve of the plans
             and specifications and the contractors, or communicate its
             objections, and if Lessor has objections, the Lessor will work
             diligently with Lessee to resolve any objections such that approval
             of the plans and specifications and names of contractors is given
             within fifteen (15) days of receipt. Lessor shall be deemed to have
             approved the plans and specifications and the contractors unless
             Lessor shall have provided written notice to Lessee of Lessor's
             objections thereto within fourteen (14) days following the delivery
             thereof by Lessee to Lessor. The Lessor approved final plans and
             specifications for the Lessee Improvements are herein called the
             "Lessee Improvements Final Plans and Specifications". All
             reasonable costs involved in approving, drafting and preparing the
             Lessee Improvements Final Plans and Specifications shall be charged
             against the Improvement Allowance described below. Lessor shall
             apply for building permits to construct the Lessee Improvements and
             will submit bid requests to the two contractors selected by Lessee
             and the contractor for the Shell Building Improvements no later
             than two (2) days following approval of the Lessee Improvements
             Final Plans and Specifications. Contractors will be required to
             submit their bids no later than thirty (30) days following receipt
             of the bid request. Lessee shall have fifteen (15) days from
             receipt of all bids to select the contractor for the Lessee
             Improvements. Except for immaterial field changes, modifications to
             the Lessee Improvements Final Plans and Specifications must be made
             and accepted only by written change order or agreement signed by
             Lessor and Lessee and will constitute an amendment to this Lease.
             Lessee shall be responsible for payment in advance of all work and
             construction resulting from changes in the Lessee Improvements
             Final Plans and Specifications requested by Lessee if the
             additional cost attributable to the changes exceed the Improvement
             Allowance by more than $3.00 as described in subparagraph (c)
             below. The Lessee Improvements Final Plans and Specifications (when
             approved by Lessor and Lessee) are incorporated in this Lease by
             reference. For the purpose of this Section, an "immaterial field
             change" shall mean such field changes which are required by any
             governmental authority or changes which (i) do not affect the size,
             configuration, structural integrity, quality, character,
             architectural appearance and standard of workmanship contemplated
             in the Lessee Improvements Final Plans and Specifications, (ii)
             will not result in any default in any obligation to any person or
             violation of any governmental requirements, and (iii) the cost of
             or reduction resulting from any single field change or extra does
             not exceed $5,000.00.

             B.  Subject to the Lessee's payment obligations under (c) below,
             Lessor shall cause the Lessee Improvements to be completed in a
             good and workmanlike manner, in accordance with all applicable laws
             and regulations, and in accordance with the Lessee Improvements
             Final Plans and Specifications. Lessor shall coordinate
             construction of Lessee Improvements, keeping Lessee informed on the
             progress of the work and of any expenditures made to perform such
             work and for such services shall be paid a construction management
             fee of five percent (5%) of the Hard Costs of such Lessee
             Improvements, which fee shall be paid out of the Improvement
             Allowance (as hereinafter defined). "Hard Costs" are the costs of
             labor, material and permits and licenses necessary to construct the
             Lessee Improvements, and do not include any legal, architectural,
             management or engineering expenses. Lessor agrees that all
             construction contracts and architectural contracts shall provide
             that the general contractor and architect for the project shall
             provide status reports and other reports relating to the
             construction of the Lessee Improvements to Lessee as well as to
             Lessor, and Lessee shall have the right at any and all times to
             inspect the Lessee Improvements at all stages of construction.
             Lessor agrees to cooperate with Lessee on any changes to the Lessee
             Improvements and agrees to provide to Lessee copies of all draw
             requests and the underlying documentation relating to the draw
             requests to Lessee. Lessor agrees to keep
<PAGE>

             the Leased Premises free from any and all mechanic's or
             materialman's liens and to pay promptly for all work to be
             performed relative to the construction project. In the event any
             such lien attaches to the Leased Premises as a result of Lessor's
             actions, and if Lessor does not contest the lien diligently and in
             good faith or does not proceed in its effort to remove the lien,
             then, in addition to any other right or remedy of Lessee, Lessee
             may, but is not obligated to, obtain the release or otherwise
             discharge the same or to obtain a bond in satisfaction of same. Any
             amount paid by Lessee in order to release or discharge any such
             lien must be paid by Lessor to Lessee on demand.

             C.  Lessor shall provide Lessee with an improvement allowance of
             $22.00 per rentable square foot of the Leased Premises (the
             "Improvement Allowance"). The Improvement Allowance shall be paid
             out from time to time to pay for costs incurred by Lessor in
             connection with the Lessee Improvements, including costs of
             Lessee's architect and/or space planner, the construction
             management fee of five percent (5%) of the Hard Costs of
             construction, and third party contractors as the Lessee
             Improvements progress. Lessee shall pay those costs of construction
             of the Lessee Improvements in excess of the Improvement Allowance,
             if any, and such amounts shall be paid by Lessee to Lessor within
             thirty (30) days following receipt by Lessee of a written request
             therefor from Lessor. In the event the costs and expenses of the
             Lessee Improvements shall exceed the Improvement Allowance, then at
             the option of Lessee and upon written request by Lessee and
             approval by Lessor's mortgagee/lender, the Lessor shall fund up to
             $3.00 per rentable square foot within the Leased Premises of such
             excess amounts and such excess amounts so funded by Lessor shall be
             paid by Lessee to Lessor as additional monthly rent. The amount to
             be added on a monthly basis to Base Rent shall be that monthly
             amount necessary to fully amortize, on a straight line basis, the
             excess amount over the term of this Lease at a ten percent (10%)
             interest rate.

       6.02  Additional Lessee Improvements. Except as provided in Section 6.01
above, Lessee shall not make or allow to be made any material alterations or
physical additions in or to the Leased Premises without complying with all
local, state and federal ordinances, laws, statutes and without first obtaining
the written consent of Lessor, which consent may not be unreasonably withheld.
In any event, Lessee shall provide Lessor with a copy of the plans and
specifications for any such alterations or improvements. Any alterations,
physical additions or improvements to the Leased Premises (including Lessee
Improvements) made by Lessor or Lessee become the property of Lessor and must be
surrendered to Lessor upon the termination of this Lease without credit to
Lessee. This clause does not apply to moveable equipment, trade fixtures,
personal property or furniture owned by Lessee, which may be removed by Lessee
at the end of the term of this Lease if Lessee is not then in default, if such
equipment and furniture are not then subject to any other rights, liens and
interest of Lessor and such removal can be accomplished without material damage
to the Leased Premises and, if there shall exist any damage caused by such
removal, such damage shall be repaired by Lessee. Upon completion of any such
work by Lessee, Lessee shall provide Lessor with "as built plans", copies of all
construction contracts and proof of payment for all labor and materials.
Notwithstanding the above, Lessee shall be allowed, without prior approval of
Lessor, to make $5,000.00 in non-structural alterations in any one calendar
year, not to exceed an aggregate of $25,000.00 over the initial term of the
Lease.

       6.03  Mechanic's Lien. Lessee will not permit any mechanic's or
materialman's lien(s) or other lien to be placed upon the Leased Premises or the
Building and nothing in the Lease is intended in any way to constitute the
consent by (or request of) Lessor, express or implied, by inference or
otherwise, to any person for the performance of any labor or the furnishing of
any materials to the Leased Premises, or any part that would give the rise to
any mechanic's or materialman's or other lien against the Leased Premises. In
the event any such lien attaches to the Leased Premises as a result of Lessee's
actions, and if Lessee does not contest the lien diligently and in good faith or
does not succeed in its effort to remove the lien, then, in addition to any
other right or remedy of Lessor, Lessor may, but is not obligated to, obtain the
release or otherwise discharge the same or to obtain a bond in satisfaction of
same. Any amount paid by Lessor in order to release or discharge any such lien
must be paid by Lessee to Lessor on demand as additional rent.
<PAGE>

                     ARTICLE 7.00 - CASUALTY AND INSURANCE

          7.01  Substantial Destruction. If the Leased Premises or any part
thereof are damaged by fire or other casualty, Lessee shall give prompt written
notice thereof to Lessor. 1) If the Leased Premises are totally destroyed by
fire or other casualty, 2) if the Leased Premises are damaged so that rebuilding
cannot reasonably be completed within one hundred eighty (180) days after the
date of written notification by Lessee to Lessor of the destruction, 3) if the
Leased Premises are part of a Building which is substantially destroyed (even
though the Leased Premises are not totally or substantially destroyed), 4) if
the Leased Premises or Building is damaged by fire or other casualty and
applicable law would prevent rebuilding to substantially the condition prior to
such fire or casualty, 5) if any mortgagee requires the insurance proceeds
payable as a result of such casualty to be applied to the payment of the
mortgage debt or 6) the Leased Premises are materially damaged and less than two
(2) years remain on the Term on the date of such casualty, Lessor or Lessee may
at their option terminate this Lease by providing the other written notice
thereof within sixty (60) days of such casualty and all obligations under the
Lease shall terminate as of the date of the casualty; provided, however, Lessee
shall not have the right to terminate this Lease if Lessor has theretofore
commenced and is diligently pursuing rebuilding.

     7.02  Partial Destruction. If this Lease is not terminated under Section
7.01, Lessor shall at its sole risk and expense proceed with reasonable
diligence to rebuild or repair the Building or other improvements to
substantially the same condition in which they existed prior to the damage,
provided, Lessor has no obligation to repair or rebuild Lessee's furniture,
fixtures or personal property. If the destruction was caused by an act or
omission of Lessee, its employees, agents, or invitees, Lessee shall pay Lessor
the difference between the actual cost of rebuilding or repairing the Leased
Premises and any insurance proceeds received by Lessor. If the Leased Premises
are to be rebuilt or repaired and are untenantable in whole or in part following
the damage, either because of the damage or the rebuilding or repairing, and the
damage or destruction was not caused or substantially contributed to by any act
or negligence of Lessee, its agents, employees, invitees or those for whom
Lessee is responsible, the rent payable under this Lease during the period for
which the Leased Premises are untenantable will be adjusted to such an extent as
may be fair and reasonable under the circumstances. If Lessor fails to complete
the necessary repairs or rebuilding within one hundred fifty days from the date
of the destruction, Lessee may at its option terminate this Lease by delivering
written notice of termination to Lessor, whereupon all rights and obligations
under this Lease cease to exist. If any damage or destruction occurs to the
Leased Premises during the last twenty-four (24) months of the Lease term,
Lessor may elect to terminate this Lease as of the date Lessee notifies Lessor
of such damage. Lessor and Lessee hereby waive the provisions of any law from
time to time in effect during the Term relating to the effect upon leases of
partial or total destruction of Leased property and agree that their respective
rights in the event of damage or destruction are those specifically set forth
herein.

     7.03  Property Insurance. Lessor shall at all times during the term of this
Lease maintain a policy or policies of insurance with the premiums paid in
advance, issued by and binding upon some solvent insurance company having an "A"
rating or better, insuring the Building against all risk of direct physical loss
in an amount equal to the full replacement cost of the Building structure and
its improvements as of the date of the loss, providing protection against all
perils, including, without limitations fire, extended coverage, vandalism,
malicious mischief, a standard mortgagee clause and rental coverage; provided,
Lessor is not obligated in any way or manner to insure any personal property
(including, but not limited to, any furniture, machinery, goods or supplies) of
Lessee upon or within the Leased Premises, any fixtures installed or paid for by
Lessee upon or within the Leased Premises, or any improvements which Lessee may
construct on the Leased Premises. The rental insurance policy will be for the
full rental value for a period of one year, which insurance also covers real
estate taxes, insurance and other amounts which might be due Lessor from Lessee
pursuant to the terms of this Lease. Lessee agrees that it is not entitled to
the proceeds of any policy of insurance maintained by Lessor even if the cost of
such insurance is borne by Lessee as set forth in Article 2.00. Notwithstanding
the foregoing, in the event Lessor has a net worth in excess of $50,000,000, it
shall be entitled to self insure against all risk provided for in this paragraph
in lieu of obtaining the insurance set forth herein.

     7.04  Waiver of Subrogation. ANYTHING IN THIS LEASE TO THE CONTRARY NOT
WITHSTANDING, LESSOR AND LESSEE HEREBY WAIVE AND RELEASE EACH OTHER OF AND FROM
ANY AND ALL RIGHT OF RECOVERY, CLAIM, ACTION OR CAUSE OF ACTION, AGAINST EACH
OTHER, THEIR AGENTS, OFFICERS AND EMPLOYEES, FOR ANY LOSS OR DAMAGE THAT MAY
OCCUR TO THE LEASED PREMISES, IMPROVEMENTS TO THE BUILDING OF WHICH THE LEASED
PREMISES ARE A PART, OR PERSONAL PROPERTY WITHIN THE
<PAGE>

BUILDING, BY REASON OF FIRE, EXPLOSION, OR ANY OTHER OCCURRENCE, REGARDLESS OF
CAUSE OR ORIGIN, INCLUDING NEGLIGENCE OF LESSOR OR LESSEE AND THEIR AGENTS,
OFFICERS AND EMPLOYEES. LESSOR AND LESSEE AGREE IMMEDIATELY TO GIVE THEIR
RESPECTIVE INSURANCE COMPANIES WHICH HAVE ISSUED POLICIES OF INSURANCE COVERING
ALL RISK OF DIRECT PHYSICAL LOSS, WRITTEN NOTICE OF THE TERMS OF THE MUTUAL
WAIVERS CONTAINED IN THIS SECTION AND TO HAVE THE INSURANCE POLICIES PROPERLY
ENDORSED, IF NECESSARY, TO PREVENT THE INVALIDATION OF THE INSURANCE COVERAGE BY
REASON OF THE MUTUAL WAIVERS.

     7.05  Hold Harmless. Lessor will not be liable to Lessee's employees,
agents, invitees, licensees or visitors, or to any other person, for an injury
to person or damage to property on or about the Leased Premises caused by any
act or omission of Lessee, its agents, servants or employees, any tenant in the
Building of which the Leased Premises are a part, or of any other person
entering upon the Leased Premises under express or implied invitation by Lessee,
the failure or cessation of any service provided by Lessor (including security
service and devices or caused by leakage of gas, oil, water or steam or by
electricity emanating from the Leased Premises) except as provided in this
Lease. Lessee agrees to indemnify and hold harmless Lessor of and from any loss,
attorney's fees, expenses or claims arising out of any such damage or injury
except for damages or injury caused by Lessor's negligence, recklessness or
willful misconduct.

     7.06  A.  At all times commencing on and after the earlier of the
           Commencement Date and the date Lessee or its agents, employees or
           contractors enters the Leased Premises for any purpose, Lessee shall
           carry and maintain, at its sole cost and expense:

               1. Commercial General Liability Insurance applicable to the
               Leased Premises and its appurtenances providing, on an occurrence
               basis, a minimum combined single limit of Two Million Dollars
               ($2,000,000.00), with a contractual liability endorsement
               covering Lessee's indemnity obligations under this Lease;

               2. All Risks of Physical Loss Insurance written at replacement
               cost value and with a replacement cost endorsement covering all
               of Lessee's personal property and improvements in the Leased
               Premises;

               3. Workers' Compensation Insurance as required by the state in
               which the Leased Premises is located and in amounts as may be
               required by applicable statute;

               4. Business interruption or loss of income insurance in amounts
               satisfactory to Lessor; and

               5. Whenever good business practice, in Lessor's reasonable
               judgment, indicates the need of additional insurance coverage or
               different types of insurance in connection with the Leased
               Premises or Lessee's use and occupancy thereof, Lessee shall,
               upon request, obtain such insurance at Lessee's expense and
               provide Lessor with evidence thereof.

           B.  Before any repairs, alterations, additions, improvements, or
           construction are undertaken by or on behalf of Lessee, Lessee shall
           carry and maintain, at its expense, or Lessee shall require any
           contractor performing work on the Leased Premises to carry and
           maintain, at no expense to Lessor, in addition to Workers'
           Compensation Insurance as required by the jurisdiction in which the
           Building is located, All Risk Builder's Risk Insurance in the amount
           of the replacement cost of any alterations, additions or improvements
           (or such other amount reasonably required by Lessor) and Commercial
           General Liability Insurance (including, without limitation,
           Contractor's Liability coverage, Contractual Liability coverage and
           Completed Operations coverage,) written on an occurrence basis with a
           minimum combined single limit of Two Million Dollars ($2,000,000.00)
           and adding "the named Lessor hereunder (or any successor thereto),
           and its respective members, principals, beneficiaries, partners,
           officers, directors, employees, agents and any Mortgagee(s)", and
           other designees of Lessor as the interest of such designees appear,
           as additional insureds (collectively referred to as the "Additional
           Insureds").
<PAGE>

           C.  Any company writing any insurance which Lessee is required to
           maintain or cause to be maintained pursuant to the terms of this
           Lease (all such insurance as well as any other insurance pertaining
           to the Leased Premises or the operation of Lessee's business therein
           being referred to as "Lessee's Insurance"), as well as the form of
           such insurance, are at all times subject to Lessor's reasonable
           approval, and each such insurance company must have an A.M. Best
           rating of "A-" or better and be licensed and qualified to do business
           in the state in which the Leased Premises are located. All policies
           evidencing Lessee's Insurance (except for Workers' Compensation
           Insurance) must specify Lessee as named insured and the Additional
           Insureds as additional insureds. Provided that the coverage afforded
           Lessor and any designees of Lessor is not reduced or otherwise
           adversely affected, all of Lessee's Insurance may be carried under a
           blanket policy covering the Leased Premises and any other of Lessee's
           locations. All policies of Lessee's Insurance must contain
           endorsements requiring that the insurer(s) give Lessor and its
           designees at least thirty (30) days' advance written notice of any
           change, cancellation, termination or lapse of said insurance. Lessee
           shall be solely responsible for payment of premiums for all of
           Lessee's Insurance. Lessee shall deliver to Lessor at least fifteen
           (15) days prior to the time Lessee's Insurance is first required to
           be carried by Lessee, and upon renewals at least fifteen (15) days
           prior to the expiration of any such insurance coverage, certified
           copies of all policies procured by Lessee in compliance with its
           obligations under this Lease. The limits of Lessee's Insurance do not
           in any manner limit Lessee's liability under this Lease.

           D.  Lessee shall not do or fail to do anything in, upon or about the
           Leased Premises which will (1) violate the terms of any of Lessor's
           insurance policies; (2) prevent Lessor from obtaining policies of
           insurance acceptable to Lessor or any Mortgagees; or (3) result in an
           increase in the rate of any insurance on the Leased Premises, the
           Building, any other property of Lessor or of others within the
           Building. In the event of the occurrence of any of the events set
           forth in this Section, Lessee shall pay Lessor upon demand, as
           additional rent, the cost of the amount of any increase in any such
           insurance premium, provided that the acceptance by Lessor of such
           payment may not be construed to be a waiver of any rights by Lessor
           in connection with a default by Lessee under the Lease. If Lessee
           fails to obtain the insurance coverage required by this Lease, Lessor
           may, at its option, obtain such insurance for Lessee, and Lessee
           shall pay, as additional rent, the cost of all premiums thereon and
           all of Lessor's costs associated therewith.

                          ARTICLE 8.00 - CONDEMNATION

     8.01  Substantial Taking. If all or a substantial portion of the Leased
Premises or a substantial portion of the Building of which the Leased Premises
are a part (even though the Leased Premises are not taken) are taken for any
public or quasi-public use under any governmental law, ordinance or regulation,
or by right of eminent domain or by purchase in lieu thereof, and the taking
would prevent or materially interfere with the use of the Leased Premises or the
Building of which the Leased Premises are a part for the purpose for which it is
then being used, then Lessor and Lessee have the option to terminate this Lease
and to abate the rent during the unexpired portion of this Lease effective on
the date title or physical possession is taken by the condemning authority,
whichever occurs first. All proceeds of any taking are the sole property of
Lessor and Lessee agrees that Lessee is not entitled to any condemnation award
or proceeds in lieu thereof.

     8.02  Partial Taking. If a portion of the Leased Premises or a portion of
the Building of which the Leased Premises are a part are taken for any public or
quasi-public use under any governmental law, ordinance or regulation, or by
right of eminent domain or by purchase in lieu thereof, and this Lease is not
terminated as provided in Section 8.01 above, Lessor shall at Lessor's sole risk
and expense, restore and reconstruct the Building and other improvements on the
Leased Premises to the extent necessary to make it reasonably tenantable;
provided, if the damages received by Lessor are insufficient to cover the costs
of restoration, Lessor may terminate this Lease. The rent payable under this
Lease during the unexpired portion of the term will be adjusted to such an
extent as may be fair and reasonable under the circumstances. All proceeds of
any taking are the sole property of Lessor and Lessee agrees that Lessee is not
entitled to any condemnation award or proceeds in lieu thereof.
<PAGE>

                     ARTICLE 9.00 - ASSIGNMENT OR SUBLEASE

     9.01  Lessor Assignment. Lessor may sell, transfer or assign, in whole or
in part, its rights and obligations under this Lease and in the Leased Premises.
Any such sale, transfer or assignment will release Lessor from any and all
liabilities under this Lease arising after the date of such sale, assignment or
transfer, so long as such transferee or assignee assumes the obligations of
Lessor hereunder.

     9.02  Lessee Assignment. Except for an assignment to an affiliate and
except in the case of a merger or consolidation by Lessee with or into another
entity, Lessee shall not assign, in whole or in part, this Lease, or allow it to
be assigned, in whole or in part, or mortgage or pledge the same or sublet the
Leased Premises, in whole or in part, without the prior written consent of
Lessor which consent may not be unreasonably withheld, and in no event will any
such assignment or sublease ever release Lessee or any guarantor from any
obligation or liability hereunder unless consented to by Lessor. No assignee or
sublessee of the Leased Premises or any portion thereof may assign or sublet the
Leased Premises or any portion thereof.

     9.03  Conditions of Assignment. If Lessee desires to assign or sublet all
or any part of the Leased Premises or grant any license, concession or other
right of occupancy of any portion of the Leased Premises, it must so notify
Lessor at least thirty days in advance of the date on which Lessee desires to
make such assignment or sublease. Lessee must provide Lessor with a copy of the
proposed assignment or sublease and such information as Lessor might reasonably
request concerning the proposed sublessee or assignee to allow Lessor to make
informed judgments as to the financial condition, reputation, operations and
general desirability of the proposed sublessee or assignee. Within fifteen days
after Lessor's receipt of Lessee's proposed assignment or sublease and all
required information concerning the proposed sublessee or assignee, Lessor may,
in its reasonable discretion, either: (1) consent to the proposed assignment or
sublease, or (2) refuse to consent to the proposed assignment or sublease, which
refusal is deemed to have been exercised unless Lessor gives Lessee written
notice providing otherwise. Upon the occurrence of an event of default, if all
or any part of the Leased Premises are then assigned or sublet, Lessor, in
addition to any other remedies provided by this Lease or provided by law, may,
at its option, collect directly from the assignee or sublessee all rents
becoming due to Lessee by reason of the assignment or sublease, and Lessor will
be entitled to a security interest in all properties on the Leased Premises to
secure payment of such sums. Lessee agrees that any collection directly by
Lessor from the assignee or sublessee is not intended to constitute a novation
or a release of Lessee or any guarantor from the further performance of its
obligations under this Lease.

     9.04  Subordination. Lessee accepts this Lease subject and subordinate to
any recorded mortgage or deed of trust lien presently existing or hereafter
created upon the Building or project of which the Leased Premises are a part
(provided, however, that any such mortgagee may, at any time, subordinate such
mortgage, deed of trust or other lien to this Lease) and to all existing
recorded restrictions, covenants, easements and agreements with respect to the
Building and to any renewals thereof. Lessee agrees that this clause is self-
operative and no further instrument of subordination is required to effect such
subordination. Lessor is hereby irrevocably vested with full power and authority
to subordinate Lessee's interest under this Lease to any first mortgage or deed
of trust lien hereafter placed on the Leased Premises, and Lessee agrees upon
demand to execute additional reasonable instruments subordinating this Lease as
Lessor may require. If the interests of Lessor under this Lease are transferred
by reason of foreclosure or other proceedings for enforcement of any first
mortgage or deed of trust lien on the Leased Premises, Lessee is bound to the
transferee (sometimes called the "Purchaser") at the option of the Purchaser,
under the terms, covenants and conditions of this Lease for the balance of the
term remaining, including any extensions or renewals, with the same force and
effect as if the Purchaser were Lessor under this Lease, and, if requested by
the Purchaser, Lessee agrees to attorn to the Purchaser, including the first
mortgagee under any such mortgage if it be the Purchaser, as its Lessor. Lessee
will not be entitled to any credits as against Purchaser any prepaid rents or
offsets against or credits due from Lessor, except as provided under the terms
of any non-disturbance agreement provided pursuant to Section 13.14 of this
Lease.

     9.05  Estoppel Certificates. Lessee agrees to furnish, from time to time,
within ten (10) days after receipt of a request from Lessor, Lessor's mortgagee
or any potential purchaser of the Building, a statement certifying, if
applicable, the following: Lessee is in possession of the Leased Premises; the
Leased Premises are acceptable; the Lease is in full force and effect; the Lease
is unmodified; Lessee claims no present charge, lien, or claim of offset against
rent; the rent is paid for the current month, but is not prepaid for more than
one month and will not be prepaid for more than one month in advance; there is
no existing default by reason of some act or
<PAGE>

omission by Lessor; and such other matters as may be reasonably required by
Lessor, Lessor's mortgagee or any potential purchaser. Lessee's failure to
deliver such statement, in addition to being a default under this Lease, may be
deemed to establish conclusively that this Lease is in full force and effect
except as declared by Lessor, that Lessor is not in default of any of its
obligations under this Lease and that Lessor has not received more than one
month's rent in advance. Any notice and cure provisions set forth in any other
part of this Lease does not apply to a default of this Section 9.05.

                              ARTICLE 10 - LIENS

     10.01  Landlord's Lien. As security for payment of rent, damages and all
other payments required to be made by this Lease, Lessee hereby grants to Lessor
a lien upon all property of Lessee now or subsequently located upon the Leased
Premises and Lessee agrees not remove such property from the Leased Premises
except in the ordinary course of business, provided at the time of such removal
Lessee is not in default. If Lessee abandons or vacates any substantial portion
of the Leased Premises or is in default in the payment of any rentals, damages
or other payments required to be made by this Lease or is in default of any
other provision of this Lease, Lessor may enter upon the Leased Premises, by
picking or changing locks if necessary, and take possession of all or any part
of the personal property, and may sell all or any part of the personal property
at a public or private sale, in one or successive sales, with or without notice,
to the highest bidder for cash, and, on behalf of Lessee, sell and convey all or
part of the personal property to the highest bidder, delivering to the highest
bidder all of Lessee's title and interest in the personal property sold. The
proceeds of the sale of the personal property shall be applied by Lessor toward
the reasonable costs and expenses of the sale, including attorney's fees, and
then toward the payment of all sums then due by Lessee to Lessor under the terms
of this Lease. Any excess remaining will be paid to Lessee or any other person
entitled thereto by law.

     10.02  Uniform Commercial Code. This Lease is intended as and constitutes a
security agreement within the meaning of the Uniform Commercial Code of the
state in which the Leased Premises are situated. Lessor, in addition to the
rights prescribed in this Lease, has all of the rights, titles, liens and
interests in and to Lessee's property, now or hereafter located upon the Leased
Premises, which may be granted a secured party, as that term is defined, under
the Uniform Commercial Code to secure to Lessor payment of all sums due and the
full performance of all Lessee's covenants under this Lease. Lessee will on
request execute and deliver to Lessor a financing statement for the purpose of
perfecting Lessor's security interest under this Lease or Lessor may file this
Lease or a copy thereof as a financing statement. Unless otherwise provided by
law and for the purpose of exercising any right pursuant to this Section, Lessor
and Lessee agree that reasonable notice has been given if such notice is given
by ten days written notice, certified mail, return receipt requested, to Lessor
or Lessee at the addresses specified herein.

     10.03  Landlord's Lien Waiver. Upon request by Lessee, Lessor will execute
a lien waiver in favor of Lessee's lender in the form prescribed by Lessee's
lender.

                       ARTICLE 11 - DEFAULT AND REMEDIES

     11.01  Default by Lessee. The following are events of default by Lessee
under this Lease:

            A.  Lessee fails to pay, within ten (10) days of when due, any
            installment of rent or any other payment required pursuant to this
            Lease, and such failure shall be continuing five (5) days following
            written notice (which notice may include the cancellation notice
            described in Section 11.02(E) hereof) thereof from Lessor to Lessee;
            provided, however, in no event shall Lessee have the right to
            receive or Lessor have the obligation to provide, as a prerequisite
            to an event of default, more than two (2) written notices within any
            twelve (12) month period;

            B.  Lessee fails to comply with any term, provision or covenant of
            this Lease, other than the payment of rent and fails to cure the
            failure within thirty (30) days of receipt of written notice (which
            notice may include the cancellation notice described in Section
            11.02(E) hereof) from Lessor;

            C.  Lessee or any guarantor of Lessee's obligations hereunder files
            a petition or is adjudged bankrupt or insolvent under any applicable
            federal or state bankruptcy or insolvency law, or
<PAGE>

            admits that it cannot meet its financial obligations as they become
            due; or a receiver or trustee is appointed for all or substantially
            all of the assets of Lessee or such guarantor; or Lessee or any
            guarantor of Lessee's obligations hereunder makes a transfer in
            fraud of creditors or makes an assignment for the benefit of
            creditors; or

            D.  Lessee does or permits to be done any act which results in a
            lien being filed against the Leased Premises or the Building and
            Lessee fails to contest the lien diligently and in good faith or
            does not prevail, within sixty (60) days of the date the lien is
            filed, in its efforts to remove the lien.

     11.02  Remedies for Lessee's Default. Upon the occurrence of any event of
default set forth in this Lease, Lessor is entitled to pursue any one or more of
the remedies set forth herein without any notice or demand.

            A.  Without declaring the Lease terminated, Lessor may enter upon
            and take possession of the Leased Premises, by picking or changing
            locks if necessary, and lock out, expel or remove Lessee and any
            other person who may be occupying all or any part of the Leased
            Premises without being liable for any claim for damages, and relet
            the Leased Premises on behalf of Lessee and receive the rent
            directly by reason of the reletting; provided however, that Lessor
            has no obligation to relet the Leased Premises so as to mitigate the
            amount for which Lessee is liable. Lessee agrees to pay Lessor on
            demand any deficiency that may arise by reason of any reletting of
            the Leased Premises; further, Lessee agrees to reimburse Lessor for
            any reasonably expenditures made by it in order to relet the Leased
            Premises, including, but not limited to, leasing commissions, lease
            incentives, remodeling and repair costs.

            B.  Without declaring the Lease terminated, Lessor may enter upon
            the Leased Premises, by picking or changing locks if necessary,
            without being liable for any claim for damages, except for damages
            arising from Lessor's negligence, recklessness or willful
            misconduct, and do whatever Lessee is obligated to do under the
            terms of this Lease. Lessee agrees to reimburse Lessor on demand for
            any expenses which Lessor may incur in effecting compliance with
            Lessee's obligations under this Lease.

            C.  Lessor may terminate this Lease, in which event Lessee shall
            immediately surrender the Leased Premises to Lessor, and if Lessee
            fails to surrender the Leased Premises, Lessor may, without
            prejudice to any other remedy which it may have for possession or
            arrearages in rent, enter upon and take possession of the Leased
            Premises, by picking or changing locks if necessary, and lock out,
            expel or remove Lessee and any other person who may be occupying all
            or any part of the Leased Premises without being liable for any
            claim for damages. Lessee agrees to pay on demand the amount of all
            loss and damage which Lessor may suffer by reason of the termination
            of this Lease under this Section, including without limitation, loss
            and damage due to the failure of Lessee to maintain and or repair
            the Leased Premises as required hereunder and/or due to the
            inability to relet the Leased Premises on terms satisfactory to
            Lessor or otherwise, and any reasonable expenditures made by Lessor
            in order to relet the Leased Premises, including, but not limited
            to, leasing commissions, lease incentives, and remodeling and repair
            costs; provided however, that Lessor will have no obligation to
            relet the Leased Premises so as to mitigate the amount for which
            Lessee is liable. In addition, upon termination Lessor may collect
            from Lessee the value of all future rentals required to be paid
            under this Lease from the date Lessor terminates the Lease until the
            original termination date in accordance with applicable law less
            amounts collected as rent by Lessor if the Leased Premises are re-
            let. Notwithstanding anything contained in this Lease to the
            contrary, this Lease may be terminated under this section by Lessor
            only by mailing or delivering written notice of such termination to
            Lessee, and no other act or omission of Lessor constitutes a
            termination of this Lease.

            D.  In the event that Lessor exercises its remedy to lock out Lessee
            in accordance with any provision of this Lease, Lessee agrees that
            no notice is required to be posted by Lessor on any door to the
            Leased Premises (or elsewhere) disclosing the reason for such action
            or any other information, and that Lessor is not obligated to
            provide a key to the changed lock to Lessee unless Lessee has first:
<PAGE>

                  1.    brought current all payments due to Lessor under this
                  Lease (unless Lessor has terminated this Lease, in which event
                  payment of all past due amounts do not obligate Lessor to
                  provide a key);

                  2.    fully cured and remedied to Lessor's reasonable
                  satisfaction all other defaults of Lessee under this Lease
                  (unless Lessee has abandoned or vacated the Leased Premises,
                  in which event Lessor is not obligated to provide the new key
                  to Lessee under any circumstances); and

                  3.    provided Lessor with additional security deposit and
                  assurances reasonably satisfactory to Lessor that Lessee
                  intends to and is able to meet and comply with its future
                  obligations under this Lease, both monetary and nonmonetary.
                  Lessor may, upon written request by Lessee, at Lessor's
                  convenience, upon receipt by Lessor of an amount necessary to
                  reimburse itself for time and expense in providing such
                  service, and upon Lessee's execution and delivery of such
                  waivers and indemnities as Lessor may require at Lessor's
                  option either:

                        a.  escort Lessee or its specifically authorized
                        employees or agents to the Leased Premises to retrieve
                        personal belongings of Lessee's employees and property
                        of Lessee that is not subject to a Security Interest
                        provided in this Lease; or

                        b.  obtain from Lessee a list of such property and
                        arrange for such items to be removed from the Leased
                        Premises and made available to Lessee at such place at
                        such time as Lessor may designate, provided however,
                        that if Lessor elects option (ii), then Lessee shall pay
                        Lessor in cash in advance, the estimated costs that
                        Lessor may incur upon moving and storage charges
                        theretofore incurred by Lessor with respect to such
                        property. THE PROVISIONS OF THIS ARTICLE ARE INTENDED TO
                        OVERRIDE AND SUPERSEDE ANY CONFLICTING PROVISIONS OF THE
                        TEXAS PROPERTY CODE AND ANY AMENDMENTS OR SUCCESSOR
                        STATUTES THERETO, AND OF ANY OTHER LAW, TO THE MAXIMUM
                        EXTENT PERMITTED BY THE LAW.

              E.  Notwithstanding any other remedy set forth in this Lease, if
              Lessor has made rent concessions of any type or character, or
              waived any base rent (i.e. given free rent), and Lessee fails to
              take possession of the Leased Premises on the Commencement Date or
              there occurs a Lessee event of default at any time during the term
              of this Lease, the rent concessions, including any waived base
              rent, are canceled and the amount of the base rent or other rent
              concessions are due and payable immediately as if no rent
              concessions or waiver of any base rent had ever been granted;
              provided, however, in the event of a default under 11.01(A) or
              11.02(B) hereof, that in order for such cancellation of rent
              concessions to be effective, Lessor must give Lessee express
              notice of the free rent cancellation in the written notice
              described in Section11.01(A) and 11.01(B). A rent concession or
              waiver of the base rent will not relieve Lessee of any obligation
              to pay any other charge due and payable under this Lease including
              without limitation any sums due under Section 2.02 herein.

              F.  If Lessor exercises any of its rights provided in this Article
              11 and Lessee subsequently cures such default, Lessor is entitled
              to receive a service charge of $500.00 from Lessee for its time
              and expense, in addition to any other amounts owed hereunder,
              prior to allowing the Lessee to reenter and reoccupy the Leased
              Premises.

              G.  Lessee hereby expressly waives any and all rights of
              redemption granted by or under any present or future laws in the
              event of Lessee being evicted or dispossessed for any cause, or in
              the event of Lessor obtaining possession of the Leased Premises by
              reason of the violation by Lessee of any of the covenants and
              conditions of this Lease or otherwise. The rights given to Lessor
              herein are in addition to any rights that may be given to Lessor
              by any statute or otherwise.
<PAGE>

              H.  Lessor's pursuit of any remedy specified in this Lease will
              not constitute an election to pursue that remedy only, nor
              preclude Lessor from pursuing any other remedy available at law or
              in equity, nor constitute a forfeiture or waiver of any rent or
              other amount due to Lessor as described herein.

              I.  If Lessee or any guarantor of Lessee's obligations hereunder
              is the subject of any insolvency, bankruptcy, receivership,
              dissolution, reorganization or similar proceeding, federal or
              state, voluntary or involuntary, under any present or future law
              or act, Lessor is entitled to the automatic and absolute lifting
              of any automatic stay as to the enforcement of its remedies under
              this Lease, including specifically the stay imposed by Section 362
              of the United States Federal Bankruptcy Code, as amended. Lessee
              hereby consents to the immediate lifting of any such automatic
              stay, and may not contest any motion by Lessor to lift such stay.
              Lessee expressly acknowledges that the Leased Premises is not now
              and will never be necessary to any plan or reorganization of any
              type.

       11.03  Lessor's Liability. The liability of Lessor to Lessee for any
default by Lessor under the terms of this Lease is limited to Lessee's actual
direct, but not consequential, damages therefor and is recoverable only from the
interest of Lessor in the Building, and Lessor is not personally liable for any
deficiency.

                          ARTICLE 12.00 - DEFINITIONS

       12.01  Abandon. "Abandon" means the vacating of all or a substantial
portion of the Leased Premises by Lessee or any approved sublessee, whether or
not Lessee or any approved sublessee is in default of the rental payments due
under this Lease;

       12.02  Building. "Building" as used in this Lease means the building
described in Section 1.02, including the Leased Premises and the land upon which
the Building is situated.

       12.03  Commencement Date. "Commencement Date" is the date set forth in
Section 1.03. The Commencement Date constitutes the commencement of the term of
this Lease for all purposes, whether or not Lessee has actually taken
possession.

                        ARTICLE 13.00 - MISCELLANEOUS

       13.01  Waiver. Failure of Lessor to declare an event of default
immediately upon its occurrence, or delay in taking any action in connection
with an event of default, will not constitute a waiver of the default, but
Lessor has the right to declare the default at any time and take such action as
is lawful or authorized under this Lease. Pursuit of any one or more of the
remedies set forth in Article 11.00 or Article 12.00 above will not preclude
pursuit of any one or more of the other remedies provided elsewhere in this
Lease or provided at law or in equity, nor will pursuit of any remedy constitute
forfeiture or waiver of any rent or damages accruing to Lessor by reason of the
violation of any of the terms, provisions or covenants of this Lease. Lessee
agrees that failure by Lessor to enforce one or more of the remedies provided
upon an event of default will not constitute a waiver of the default or of any
other violation or breach of any of the terms, provisions and covenants
contained in this Lease.

       No act or thing done by Lessor or its agents during the Lease Term may be
deemed an acceptance of an attempted surrender of the Leased Premises, and no
agreement to accept a surrender of the Leased Premises will be valid unless made
in writing and signed by Lessor. No reentry or taking possession of the Leased
Premises by Lessor may be construed as an election on its part to terminate this
Lease, unless a written notice of such intention, signed by Lessor, is given by
Lessor to Lessee. Notwithstanding any such reletting or reentry or taking
possession, Lessor may at any time thereafter elect to terminate this Lease for
a previous event of default. Lessee and Lessor agree that Lessor's acceptance of
rent following an event of default hereunder will not constitute Lessor's waiver
of such event of default. The failure of Lessor to enforce any of the Rules and
Regulations described in Section 3.03 against Lessee or any other Lessee in the
Building will not constitute a waiver of any such Rules and Regulations. No
waiver of any provision of this Lease is effective unless such waiver is in
writing and signed by Lessor. All rights granted to Lessor in this Lease are
cumulative of every other right or remedy which Lessor may otherwise
<PAGE>

have at law or in equity, and the exercise of one or more rights or remedies
does not prejudice or impair the concurrent or subsequent exercise of other
rights or remedies.

     13.02  Act of God. Lessor or Lessee is not required to perform any covenant
or obligation in this Lease, or be liable in damages to the other, so long as
the performance or non-performance of the covenant or obligation is delayed,
caused or prevented by Force Majeure or by the other party.

     13.03  Attorney's Fees. If either party defaults in the performance of any
of the terms, covenants, agreements or conditions contained in this Lease and
the other party places in the hands of an attorney the enforcement of all or any
part of this Lease, the collection of any rent due or to become due or recovery
of the possession of the Leased Premises, agrees to pay the non-defaulting
party's costs of collection, including reasonable attorney's fees for the
services of the attorney, whether suit is actually filed or not.

     13.04  Successors. This Lease is binding upon and inures to the benefit of
Lessor and Lessee and their respective heirs, personal representatives,
successors and assigns. It is hereby covenanted and agreed that should Lessor's
interest in the Leased Premises cease to exist for any reason during the term of
this Lease, then notwithstanding the happening of such event this Lease
nevertheless will remain unimpaired and in full force and effect, and Lessee
hereunder agrees to attorn to the then owner of the Leased Premises.

     13.05  Rent Tax. If applicable in the jurisdiction where the Leased
Premises are situated, Lessee shall pay and be liable for all rental, sales and
use taxes or other similar taxes, if any, levied or imposed by any city, state,
county or other governmental body having authority, such payments to be in
addition to all other payments required to be paid to Lessor by Lessee under the
terms of this Lease. Any such payment must be paid concurrently with the payment
of the rent, additional rent, operating expenses or other charge upon which the
tax is based as set forth above.

     13.06  Captions. The captions appearing in this Lease are inserted only as
a matter of convenience and in no way define, limit, construe or describe the
scope or intent of any Section.

     13.07  Notice. All rent and other payments required to be made by Lessee
must be paid to Lessor at the address set forth in Section 1.05. All payments
required to be made by Lessor to Lessee are payable to Lessee at the address set
forth in Section 1.05 or at any other address within the United States as Lessee
may specify from time to time by written notice. For purposes hereof, any notice
or document required or permitted to be delivered by the terms of this Lease
(other than delivery of rental payments) will be deemed to be delivered upon the
earlier of actual receipt, or (whether or not actually received) three days
after being deposited in the United States Mail, postage prepaid, certified
mail, return receipt requested, addressed to the parties at the respective
addresses set forth in Section 1.05, or transmission by facsimile and receipt of
confirmation of successful transmission by the transmitting facsimile; provided,
however, any notice given by facsimile must be followed up by notice in one of
the other manners set forth herein within five (5) days thereafter. Rental
payments will be deemed received upon actual receipt only. Except as
specifically set forth herein, in no event will notice by facsimile transmission
be proper notice under the terms of this Lease.

     13.08  Submission of Lease. Submission of this Lease to Lessee for
signature does not constitute a reservation of space or an option or offer to
lease. This Lease is not deemed effective until execution by and delivery to
both Lessor and Lessee.

     13.09  Representations, Warranties and Covenants of Lessee and Lessor.
Lessee represents, warrants and covenants that it is now in a solvent condition;
that no bankruptcy or insolvency proceedings are pending or contemplated by or
against Lessee or any guarantor of Lessee's obligations under this Lease; that
all reports, statements and other data furnished by Lessee to Lessor in
connection with this Lease are true and correct in all material respects; that
the execution and delivery of this Lease by Lessee does not contravene, result
in a breach of, or constitute a default under any contract or agreement to which
Lessee is a party or by which Lessee may be bound and does not violate or
contravene any law, order, decree, rule or regulation to which Lessee is
subject; and that there are no judicial or administrative actions, suits, or
proceedings pending or threatened against or affecting Lessee or any guarantor
of Lessee's obligations under this lease.
<PAGE>

Lessor represents, warrants and covenants that it is now in a solvent condition;
that no bankruptcy or insolvency proceedings are pending or contemplated by or
against Lessor or any guarantor of Lessor's obligations under this Lease; that
all reports, statements and other data furnished by Lessor to Lessee in
connection with this Lease are true and correct in all material respects; that
the execution and delivery of this Lease by Lessor does not contravene, result
in a breach of, or constitute a default under any contract or agreement to which
Lessee is a party or by which Lessee may be bound and does not violate or
contravene any law, order, decree, rule or regulation to which Lessor is
subject; and that there are no judicial or administrative actions, suits, or
proceedings pending or threatened against or affecting Lessor or any guarantor
of Lessor's obligations under this lease.

     13.10  Corporate Authority. If Lessee executes this Lease as a corporation,
Lessee represents and warrants that Lessee is a duly authorized and existing
corporation, that Lessee is qualified to do business in the state in which the
Leased Premises are located, that the corporation has full right and authority
to enter into this Lease, and that each person signing on behalf of the
corporation is authorized to do so. Lessee shall additionally deliver (1) a
corporate resolution authorizing execution of this Lease and confirming the
authority of those persons executing the Lease, 2) certified Articles of
Incorporation and 3) a certificate of existence and good standing from the State
of Texas or if Lessee is not incorporated in Texas, a certificate of existence
and good standing from Lessee's state of incorporation and a certificate
evidencing Lessee's authority to do business in the State of Texas.

If Lessor executes this Lease as a corporation, Lessor represents and warrants
that Lessor is a duly authorized and existing corporation, that Lessor is
qualified to do business in the state in which the Leased Premises are located,
that the corporation has full right and authority to enter into this Lease, and
that each person signing on behalf of the corporation is authorized to do so.
Lessor shall additionally deliver (1) a corporate resolution authorizing
execution of this Lease and confirming the authority of those persons executing
the Lease, 2) certified Articles of Incorporation and 3) a certificate of
existence and good standing from the State of Texas or if Lessee is not
incorporated in Texas, a certificate of existence and good standing from
Lessee's state of incorporation and a certificate evidencing Lessee's authority
to do business in the State of Texas.

     13.11  Partnership Authority. If Lessee executes this Lease as a general or
limited partnership, Lessee represents and warrants that Lessee is a duly
authorized and existing partnership, that, if applicable, Lessee is qualified to
do business in the state where the Leased Premises are located, that the
partnership has full right and authority to enter into this Lease, and that each
person signing on behalf of the partnership is authorized to do so. Lessee, must
additionally deliver a copy of its partnership agreement, and if a limited
partnership, a copy of its certificate of limited partnership. The party
executing the Lease on behalf of Lessee, if a corporate managing general partner
or general partner, must additionally deliver 1) a corporate resolution
authorizing execution of this Lease and confirming the authority of those
executing this Lease, 2) certified Articles of Incorporation, 3) a certificate
of existence and good standing from the State of Texas or if such party is not
incorporated in Texas, a certificate of existence and good standing from such
party's state of incorporation and a certificate evidencing such party's
authority to do business in the State of Texas.

If Lessor executes this Lease as a general or limited partnership, Lessor
represents and warrants that Lessor is a duly authorized and existing
partnership, that, if applicable, Lessor is qualified to do business in the
state where the Leased Premises are located, that the partnership has full right
and authority to enter into this Lease, and that each person signing on behalf
of the partnership is authorized to do so. Lessor, must additionally deliver a
copy of its partnership agreement, and if a limited partnership, a copy of its
certificate of limited partnership. The party executing the Lease on behalf of
Lessee, if a corporate managing general partner or general partner, must
additionally deliver 1) a corporate resolution authorizing execution of this
Lease and confirming the authority of those executing this Lease, 2) certified
Articles of Incorporation, 3) a certificate of existence and good standing from
the State of Texas or if such party is not incorporated in Texas, a certificate
of existence and good standing from such party's state of incorporation and a
certificate evidencing such party's authority to do business in the State of
Texas.

     13.12  Severability. If any provision of this Lease or the application
thereof to any person or circumstance is ever determined by a court of competent
jurisdiction to be invalid or unenforceable to any extent, Lessor and Lessee
agree that the remainder of this Lease and the application of such provisions to
other persons or circumstances will not be affected thereby and will be enforced
to the greatest extent permitted by law.
<PAGE>

     13.13  Lessor's Liability. If Lessor is in default under this Lease and, if
as a consequence of such default, Lessee recovers a money judgment against
Lessor, such judgment may be satisfied only out of the right, title and interest
of Lessor in the Leased Premises as the same may then be encumbered and neither
Lessor nor any person or entity comprising Lessor has any liability for any
deficiency. In no event does Lessee have the right to levy execution against any
property of Lessor nor any person or entity comprising Lessor other than its
interest in the Leased Premises as herein expressly provided.

     13.14  Non Disturbance Agreement. Lessor shall deliver a non-disturbance
agreement from each of Lessors mortgagees within sixty (60) days of the
execution of this Lease in form satisfactory to Lessee in its reasonable
judgment. If any new lien or mortgage is placed on the Building or Leased
Premises during the term of this Lease, Landlord will deliver additional non-
disturbance agreements as soon as practical in form satisfactory to Lessee in
its reasonable judgment.

     13.15  Notice to Mortgagees. Provided that Lessee has received prior
written notice of the name and address of such lender, Lessee shall serve
written notice of any claimed default or breach by Lessor under this Lease upon
any lender which is a beneficiary under any deed of trust or mortgage against
the Leased Premises, and no notice to Lessor is effective against Lessor unless
such notice is served upon said lender; notwithstanding anything to the contrary
contained herein, Lessee shall allow such lender the same period following
lender's receipt of such notice to cure such default or breach as is afforded
Lessor.

     13.16  No Recordation. Lessee may not record this Lease.

     13.17  Counterparts. This Lease may be executed in two or more
counterparts, and it is not necessary that any one of the counterparts be
executed by all of the parties hereto. Each fully or partially executed
counterpart may be deemed an original, but all such counterparts taken together
constitute but one and the same instrument.

     13.18  Governing Law. THIS LEASE IS INTENDED BY THE PARTIES TO BE GOVERNED
BY, AND CONSTRUED UNDER AND IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS
AND THE LAWS OF THE UNITED STATES OF AMERICA AS APPLICABLE TO TRANSACTIONS
WITHIN THE STATE OF TEXAS.

     13.19  Broker. Lessee represents and warrants that Lessee has dealt with no
broker except Providence Commercial Real Estate Services, Inc., for Lessee, and
Pruitt Realty, for Lessor, the brokers which has been identified to Lessor and
Lessee, and that, insofar as Lessee and Lessor know, no other broker negotiated
this Lease or is entitled to any commission in connection herewith. Lessor
agrees to indemnify and hold harmless Lessee from and against any liability or
claim, whether meritorious or not, arising with respect to any broker whose
claim arises by, through or on behalf of Lessor. Lessee agrees to indemnify and
hold harmless Lessor from and against any liability or claim, whether
meritorious or not, arising with respect to any broker whose claim arises by,
through or on behalf of Lessee.

     13.20  Publication. Each party hereby agrees that the other has the right,
but not the obligation, at its own expense to publicize and/or advertise the
execution of this Lease and the related transaction.

     13.21  DTPA Waiver. LESSEE WAIVES ITS RIGHTS UNDER THE DECEPTIVE TRADE
PRACTICES - CONSUMER PROTECTION ACT, SECTION 17.41 ET SEQ., BUSINESS & COMMERCE
CODE, A LAW THAT GIVES CONSUMERS SPECIAL RIGHTS AND PROTECTIONS. AFTER
CONSULTATION WITH AN ATTORNEY OF LESSEE'S OWN SELECTION, LESSEE VOLUNTARILY
CONSENTS TO THIS WAIVER.

     13.22  Construction of Lease. Lessee declares that Lessee has read and
understands all parts of this Lease, including all printed parts hereof. It is
agreed that, in the construction and interpretation of the terms of this Lease,
the rule of construction that a document is to be construed most strictly
against the party who prepared the same shall not be applied, it being agreed
that both parties hereto have participated in the preparation of the final form
of this Lease. Wherever in this Lease provision is made for liquidated damages,
it is because the parties hereto acknowledge and agree that the determination of
actual damages (of which such liquidated damages are in lieu) is speculative and
difficult to determine; the parties agree that liquidated damages herein are not
a penalty.
<PAGE>

     13.23  Financial Statements. Lessee acknowledges that it has provided
Lessor with its financial statement(s) as a primary inducement to Lessor's
agreement to lease the Leased Premises to Lessee, and that Lessor has relied on
the accuracy of said financial statement(s) in entering into this Lease. Lessee
represents and warrants that the information contained in said financial
statement(s) is true, complete and correct in all material aspects, and agrees
that the foregoing representations are conditions to all of Lessor's obligations
under this Lease.

     At the request of Lessor (only upon the sale or refinancing of the
Building, or upon any extension or renewal hereof), Lessee shall, not later than
thirty (30) days following such request, furnish to Lessor a financial statement
of Lessee as of the end of the prior fiscal year accompanied by a statement of
income and expense for the year then ended, together with a certificate of the
chief financial officer, owner or partner of Lessee to the effect that the
financial statements have been prepared in conformity with generally accepted
accounting principles consistently applied and fairly present the financial
condition and results of operations of Lessee as of and for the periods covered.

     13.24  Time of Essence. With respect to all required acts of Lessee, time
is of the essence of this Lease.

     13.25  Joint and Several Liability. If there is more than one Lessee, the
obligations hereunder imposed upon Lessee are joint and several. If there is a
guarantor(s) of Lessee's obligations hereunder, the obligations of Lessee are
joint and several obligations of Lessee and each such guarantor, and Lessor need
not first proceed against Lessee hereunder before proceeding against each such
guarantor, nor will any such guarantor be released from its guarantee for any
reason whatsoever, including, without limitation, any amendment of this Lease,
any forbearance by Lessor or waiver of any of Lessor's rights, the failure to
give Lessee or any such guarantor any notices, or the release of any party
liable for the payment or performance of any of Lessee's obligations hereunder.

     13.26  Taxes and Lessee's Property. Lessee is solely liable for all taxes
levied or assessed against personal property, furniture or fixtures placed by
Lessee in the Premises. If any such taxes for which Lessee is liable are levied
or assessed against Lessor or Lessor's property and if Lessor elects to pay the
same or if the assessed value of Lessor's property is increased by inclusion of
personal property, furniture or fixtures placed by Lessee in the Premises, and
Lessor elects to pay the taxes based on such increase, Lessee shall pay Lessor
upon demand that part of such taxes for which Lessee is primarily liable
hereunder.

     13.27  Constructive Eviction. Lessee shall not be entitled to claim a
constructive eviction from the Leased Premises unless Lessee has first notified
Lessor in writing of the condition giving rise thereto, and, if the complaints
are justified, unless Lessor has failed to remedy such conditions with a
reasonable time after receipt of said notice.

             ARTICLE 14.00 - AMENDMENT AND LIMITATION OF WARRANTIES

     14.01  Entire Agreement. IT IS EXPRESSLY AGREED BY LESSEE, AS A MATERIAL
CONSIDERATION FOR THE EXECUTION OF THIS LEASE, THAT THIS LEASE, WITH THE
SPECIFIC REFERENCES TO WRITTEN EXTRINSIC DOCUMENTS, IS THE ENTIRE AGREEMENT OF
THE PARTIES; THAT THERE ARE, AND WERE, NO VERBAL REPRESENTATIONS, WARRANTIES,
UNDERSTANDINGS, STIPULATIONS, AGREEMENTS OR PROMISES PERTAINING TO THIS LEASE OR
TO THE EXPRESSLY MENTIONED WRITTEN EXTRINSIC DOCUMENTS NOT INCORPORATED IN
WRITING IN THIS LEASE.

     14.02  Amendment. THIS LEASE MAY NOT BE ALTERED, WAIVED, AMENDED OR
EXTENDED EXCEPT BY AN INSTRUMENT IN WRITING SIGNED BY LESSOR AND LESSEE.

     14.03  Limitation of Warranties. LESSOR AND LESSEE EXPRESSLY AGREE THAT
THERE ARE AND SHALL BE NO IMPLIED WARRANTIES OF MERCHANTABILITY, HABITABILITY,
FITNESS FOR A PARTICULAR PURPOSE OR OF ANY OTHER KIND ARISING OUT OF THIS LEASE,
AND THERE ARE NO WARRANTIES WHICH EXTEND BEYOND THOSE EXPRESSLY SET FORTH IN
THIS LEASE.
<PAGE>

                          ARTICLE 15.00 - SIGNATURES

     SIGNED this _______ day of April, 1999.

LESSOR:                                  LESSEE:

ACLP UNIVERSITY PARK SA, L.P.            AMERICAN TELESOURCE
a Texas limited partnership               INTERNATIONAL, INC.,
                                         a Texas corporation

BY:  ACLP UNIVERSITY PARK SA
     GP, INC., a Texas corporation

                                         By:    _______________________________
                                         Name:  _______________________________
                                         Title: _______________________________
By:  ______________________________
     Name:  Sue Shelton
     Title: Executive Vice President

                                         LESSEE ACKNOWLEDGES THAT THIS LEASE
                                         INCLUDES THE INDEMNIFICATION PROVISIONS
                                         SET FORTH IN SECTIONS 3.01, 3.06, 7.05
                                         AND 13.19 HEREOF.
<PAGE>

                             RULES AND REGULATIONS

1.   Lessor agrees to furnish Lessee two keys without charge. Additional keys
     will be furnished at a nominal charge. Lessee shall not change locks or
     install additional locks on doors without prior written consent of Lessor.
     Lessee shall not make or cause to be made duplicates of keys procured from
     Lessor without prior approval of Lessor. All keys to Leased Premises shall
     be surrendered to Lessor upon termination of this Lease.

2.   Lessee will refer all contractors, contractors representatives and
     installation technicians rendering any service on or to the Leased Premises
     for Lessee to Lessor for Lessor's approval before performance of any
     contractual service. Lessee's contractors and installation technicians
     shall comply with Lessor's rules and regulations pertaining to construction
     and installation. This provision shall apply to all work performed on or
     about the Leased Premises or project, including installation of telephones,
     telegraph equipment, electrical devices and attachments and installations
     of any nature affecting floors, walls, woodwork, trim, windows, ceilings
     and equipment or any other physical portion of the Leased Premises or
     project.

3.   Lessee shall not at any time occupy any part of the Leased Premises or
     project as sleeping or lodging quarters.

4.   Lessee shall not place, install or operate on the Leased Premises or in any
     part of the building any engine, stove or machinery, or conduct mechanical
     operations or cook thereon or therein, or place or use in or about the
     Leased Premises or project any explosives, gasoline, kerosene, oil, acids,
     caustics, or any flammable, explosive or hazardous material without written
     consent of Lessor, except that Lessee may provide a kitchen for use by its
     employees during normal business hours.

5.   Lessor will not be responsible for lost, stolen or damaged personal
     property, equipment, money or jewelry from the Leased Premises by a third
     party or the project regardless of whether such loss occurs when the area
     is locked against entry or not.

6.   No dogs, cats, fowl, or other animals shall be brought into or kept in or
     about the Leased Premises or project.

7.   Employees of Lessor shall not receive or carry messages for or to any
     Lessee or other person or contract with or render free or paid services to
     any Lessee or to any of Lessee's agents, employees or invitees.

8.   None of the parking, plaza, recreation or lawn areas, entries, exits,
     passages, doors, elevators, hallways or stairways shall be blocked or
     obstructed or any rubbish, litter, trash, or material of any nature placed,
     emptied or thrown into these areas or such area used by Lessee's agents,
     employees or invitees at any time for purposes inconsistent with their
     designation by Lessor.

9.   The water closets and other water fixtures shall not be used for any
     purpose other than those for which they were constructed, and any damage
     resulting to them from misuse, including improper disposal of any
     materials, or by the defacing or injury of any part of the Building shall
     be borne by the person who shall occasion it. No person shall waste water
     by interfering with the faucets or otherwise.

10.  No person shall disturb occupants of the Building by the use of any radios,
     record players, tape recorders, musical instruments, the making of unseemly
     noises or any unreasonable use.

11.  Nothing shall be thrown out of the windows of the Building or down the
     stairways or other passages.

12.  Lessee and its employees, agents and invitees shall park their vehicles
     only in those parking areas designated by Lessor. Lessee shall furnish
     Lessor with state automobile license numbers of Lessee's vehicles and its
     employees' vehicles within five days after taking possession of the Leased
     Premises and
<PAGE>

     shall notify Lessor of any changes within five days after such change
     occurs. Lessee shall not leave any vehicle in a state of disrepair
     (including without limitation, flat tires, out of date inspection stickers
     or license plates) on the Leased Premises or project. If Lessee or its
     employees, agents or invitees park their vehicles in areas other than the
     designated parking areas or leave any vehicle in a state of disrepair,
     Lessor, after giving written notice to Lessee of such violation, shall have
     the right to remove such vehicles at Lessee's expense.

13.  Parking in a parking garage or area shall be in compliance with all parking
     rules and regulations including any sticker or other identification system
     established by Lessor. Failure to observe the rules and regulations shall
     terminate Lessee's right to use the parking garage or area and subject the
     vehicle in violation of the parking rules and regulations to removal and
     impoundment. No termination of parking privileges or removal of impoundment
     of a vehicle shall create any liability on Lessor or be deemed to interfere
     with Lessee's right to possession of its Leased Premises. Vehicles must be
     parked entirely within the stall lines and all directional signs, arrows
     and posted speed limits must be observed. Parking is prohibited in areas
     not striped for parking, in aisles, where "No Parking" signs are posted, on
     ramps, in cross hatched areas, and in other areas as may be designated by
     Lessor. Parking stickers or other forms of identification supplied by
     Lessor shall remain the property of Lessor and not the property of Lessee
     and are not transferable. Every person is required to park and lock his
     vehicle. All responsibility for damage to vehicles or persons is assumed by
     the owner of the vehicle or its driver.

14.  Lessee shall not lay floor covering within the Leased Premises without
     written approval of the Lessor. The use of cement or other similar adhesive
     materials not easily removed with water is expressly prohibited.

15.  Lessee agrees to cooperate and assist Lessor in the prevention of
     canvassing, soliciting and peddling within the Building or project.

16.  It is Lessor's desire to maintain in the Building or project the highest
     standard of dignity and good taste consistent with comfort and convenience
     for Lessees. Any action or condition not meeting this high standard should
     be reported directly to Lessor. Your cooperation will be mutually
     beneficial and sincerely appreciated. As provided in the Lease, Lessor
     reserves the right to make such other and further reasonable rules and
     regulations as in its judgment may from time to time be necessary, for the
     safety, care and cleanliness of the Leased Premises and for the
     preservation of good order therein.

17.  The parking spaces provided to Lessee shall not be fewer than six spaces
     per 1000 rentable square feet of Leased Premises

18.  All signage must be approved by Lessor and be within Lessor's
     specifications in accordance with Section 3.02 of the Lease.
<PAGE>

                   ADDENDUM 1 TO COMMERCIAL LEASE AGREEMENT
                                 ARTICLE 16.00
                              Lessor Improvements

     16.01  Lessor Improvements. Prior to Lessee's occupancy, Lessor shall, at
its own cost and expense, construct the Building and improvements (the "Shell
Building Improvements") as generally shown on the site plan and artist's
rendering prepared by Rehler Vaughn & Koone, Inc., and attached hereto as
Exhibit "A". Lessor warrants that the Shell Building Improvements will be
generally consistent in quality with the building shown in the artist's
rendering attached as Exhibit "A" and with other buildings in Dallas, Texas,
which were shown to Lessee's representatives as samples of Lessor's projects.
The Final Shell Plans and Specifications shall be provided to Lessee on or
before June1, 1999. Lessor will begin construction of the Shell Building
Improvements no later than June 1, 1999 and shall have completed the Shell
Building Improvements to the extent to allow construction of the Lessee
Improvements no later than September 15, 1999. Except for immaterial field
changes, modifications to the Final Shell Plans and Specifications must be made
and accepted only by written change order or agreement signed by Lessor and
Lessee and will constitute an amendment to this Lease. Lessee shall be
responsible for payment in advance of all work and construction resulting from
changes in the Final Shell Plans and Specifications requested by Lessee. The
Final Shell Plans and Specifications (when approved by Lessor and Lessee) are
incorporated in this Lease by reference. For the purpose of this Section, an
"immaterial field change" shall mean such field changes which are required by
any governmental authority or changes which (i) do not affect the size,
configuration, structural integrity, quality, character, architectural
appearance and standard of workmanship contemplated in the Final Shell Plans and
Specifications, (ii) will not result in any default in any obligation to any
person or violation of any governmental requirements, and (iii) the cost of or
reduction resulting from any single field change or extra does not exceed
$20,000 and the aggregate amount of all such changes and extras does not exceed
$100,000. Lessor agrees to construct the improvements substantially in
accordance with the Final Shell Plans and Specifications, in a good and
workmanlike manner and in full compliance with all provisions of federal, state
and local authorities having jurisdiction over the Leased Premises.

                         ARTICLE 17.00 - Completion

     17.01  Completion Date.
            ---------------

            (b) If (i) this Lease is executed and delivered by Lessee by April
9, 1999, (ii) the Lessee Improvement Final Plans and Specifications are approved
by Lessor by July 15, 1999 (iii) Lessee has selected by September 1, 1999, the
contractor who will construct the Lessee Improvements, and (iv) the building
permit for the Lessee Improvements is issued by September 15, 1999, then Lessor
shall cause Substantial Completion (as defined in Section 17.04 hereof) to occur
no later than December 15, 1999 (such date being extended by the longest number
of days that the satisfaction of any of the above conditions is delayed, Force
Majeure and Lessee Delays with the date, as extended, being hereinafter referred
to as the "Threshold Date"). In the event that the foregoing conditions are
satisfied and Substantial Completion does not occur by the Threshold Date, then
Lessee, as Lessee's sole and exclusive remedy and measure of damages for or
related to the delay in Substantial Completion, shall have the right to receive
one day of free rent, in addition to the free rent described in Section 3.01,
for each day of unexcused delay beyond the Threshold Date, up to a maximum of
sixty (60) days, and in the event of unexcused delay beyond sixty (60) days
after the Threshold Date, the Lessee shall have the right to receive two (2)
days of free rent, in addition to the free rent described in Section 3.01, for
each day of unexercised delay beyond sixty days after the Threshold Date, and in
the event of unexcused delay beyond one hundred twenty (120) days after the
Threshold Date, the Lessee shall have the right to terminate this Lease by
written notice thereof to Lessor within ten (10) days following the one hundred
twentieth day after such Threshold Date; provided, however, in the event Lessee
fails to deliver such termination notice within such ten (10) period, the Lessee
shall be deemed to have waived any right to terminate this Lease for delay
provided in this Section.

     17.02  Force Majeure.  "Force Majeure" delay shall mean a delay caused by
            -------------
reason of fire, acts of God, unreasonable delays in transportation, embargo,
weather, strike, other labor disputes, governmental preemption of priorities or
other controls in connection with a national or other public emergency, or
shortages of fuel, supplies or labor or any similar cause not within the
reasonable control of the party claiming the benefits of any Force Majeure
provisions. The party claiming the benefits of any Force Majeure provisions
shall be required (as a condition to the effectiveness thereof) to provide
written notice of the occurrence of such Force Majeure event within ten (10)
days following such occurrence.
<PAGE>

     17.03  Lessor and Lessee Delay.

               (a)  The terms "Lessor Delays", "Delays caused by Lessor",
"Lessee Delay" or "Delays caused by Lessee" shall mean delay in completion of
construction of the Shell Building Improvements or the Lessee Improvements
caused by:

                         (1)  Unless due to the acts or omissions of the other
     party or such party's agents, employees or contractors, the respective
     party's failure to perform its design approval obligations or its
     construction period obligations by the dates or within the time periods
     shown in the Lease or this Addendum 1; and

                         (2)  Any subsequent changes, modifications or
     alterations to the final plans and specifications or the Final Tenant
     Improvement Plans and specifications which reasonably cause delay in the
     completion thereof; and

               (b)  "Lessee Delay" or "Delays caused by Lessee" shall also mean
delays due to the scope and extent of the Lessee Improvements to be constructed
by Lessor. For purposes of determining Lessee Delay under this Section, the
Lessor must provide notice to Lessee of the existence of excessive Lessee
Improvements, special design or construction considerations or other matters
which will extend the time necessary for the construction of the Lessee
Improvements beyond two (2) days; such notice to be provided by Lessor to Lessee
together with Lessor's delivery of approval and/or objections to Lessee's plans
and specifications for the Lessee Improvements from time-to-time. Such notice
shall specify the reasons for the delay and the estimated length of delay and,
unless the Lessee's plans and specifications are modified to eliminate such
items, the estimated length of the delay shall be included as a Lessee Delay.
For purposes of determining delay, the terms Lessor and Lessee shall include
their respective contractors, agents and employees. In addition, the party
claiming the benefits of such delay shall be required (as a condition to the
effectiveness thereof) to provide written notice of the occurrence of such delay
within ten (10) days following such occurrence.

               17.04     "Substantial Completion" shall mean that time when the
following conditions are satisfied:

                             (a)  Lessor secures and delivers to Lessee the
                         required temporary or permanent certificate of
                         occupancy, final inspection report or the substantial
                         equivalent under applicable state or local law relative
                         to the Shell Building Improvements and the Lessee
                         Improvements; and

                             (b)  The construction is completed in accordance
                         with the Final Shell Plans and Specifications and the
                         Lessee Improvements Final Plans and Specifications as
                         acknowledged by Lessor's architect in writing to
                         Lessee, subject to normal punch list items which will
                         not materially interfere with Lessee's ability to
                         utilize the Leased Premises for its intended purposes.
<PAGE>

                                  EXHIBIT "D"
                                  -----------
                           CERTIFICATE OF ACCEPTANCE

Building:__________________________________________________________________
Lessor:  __________________________________________________________________
Lessee:  __________________________________________________________________

This certificate is being executed pursuant to the Commercial Lease (the
"Lease") for Leased Premises (as defined in the Lease) in the Building named
above, executed on the ___ day of _______ , 1999, between Lessor and Lessee.

Lessee certifies to and agrees with Lessor and Lessor's successors, assigns,
prospective purchasers and prospective lenders that:

1.   Lessor has substantially completed all construction work and leasehold
     improvements required of Landlord under the terms of the Lease and/or any
     other agreement between Lessor and Lessee concerning the Leased Premises,
     and the Leased Premises have been delivered to Lessee in the conditional
     contemplated by Lessee, except for Defects, the presence of Hazardous
     Materials (as those terms are defined in the Lease) and punch list items.
2.   Lessee has taken possession of and has accepted the Premises, and the Base
     Rent, additional rent, and/or other charges payable under the Lease are
     presently accruing in accordance with the terms of the Lease or if not,
     will commence to accrue on the ____ day of _______ , 1999.
3.   The Lease has not been modified, altered or amended except as noted herein.
4.   There are no offsets or credits against rentals, nor have rentals been
     prepaid except as may be provided in the Lease, but in no event have
     rentals been prepaid more than thirty (30) days in advance, except for the
     7th month's rent.
5.   The Lease Term will commence on ___ day of ___________ , 1999, and will
     expire on the ____ day of _________ , ____ , unless sooner terminated or
     extended pursuant to any provision of the Lease.

Certified and Agreed to this ___ day of ________, 1999.

Lessee:_________________________
Name:___________________________
Title:__________________________

<PAGE>

                                   CONDITIONS

1.   The registration for the provision of value added services supported by
     this certificate have an indefinite term. When the service provider stops
     providing the services for its own convenience, the provider must notify
     the Ministry of Communications and Transportation.

1.   To provide value added services, the provider agrees to solely utilize
     homologated equipment and public telecommunications networks authorized by
     the Ministry of Communications and Transportation.

1.   The Ministry of Communications and Transportation shall have the ability at
     any time to make administrative technical inspections at the provider's
     facilities and request additional information related with the value added
     services registered.

1.   The service provider must notify the Ministry of Communications and
     Transportation any modification in their address, legal representative,
     addition of new services or the transmission means utilized to provide the
     services.before any changes are made.

1.   Providing false information upon registering the value added services or in
     any other request made to the Ministry of Communications and Transportation
     will be reason to initiate any sanction proceedings.

1.   The value added services provider whose registration certificate is
     attached hereto must submit to the Ministry of Communications and
     Transportation on an annual basis and within 30 days after the anniversary
     date of this certificate, a completed  "Annual Report of Value Added
     Services" for the purpose of maintaining updated information.  By not
     submitting in a timely manner the above mentioned report, it shall be
     understood as desisting to continue to provide the services and shall
     automatically generate cancellation of its registration.

1.   The exercise of the rights derived from this registration implies the
     unconditional acceptance of all the terms by the service provider.

(Illegible signature)

cc:  Lic. Carlos Casasus Lopez Hermosa - Undersecretary of Communications and
     Technological Development.

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