Document:

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                                                                   EXHIBIT 10.11

                                   AMENDMENT

AMENDMENT, made and entered into as of this 1/st/ day of November, 1999, to that
certain Consultant Agreement ("Agreement"), entered into on June 1, 1999, by and
between A. Sidney Alpert and Luminex Corporation.

WHEREAS, at this time, Luminex Corporation and Mr. Alpert, wish to revise the
terms and conditions of the Agreement.

NOW, THEREFORE, all of the terms and conditions set forth in the Agreement shall
remain in effect as stated, except as follows:

1.   The term of the Agreement shall be extended through October 31, 2000.

2.   Article 3.1 of the Agreement shall be amended by changing the phrase, "one
     working day" to "two working days."

3.   The compensation set forth in Article 4 of the Agreement shall be changed
     to the sum of Eleven Thousand Six Hundred Sixty-Six and No/100 Dollars
     ($11,666.00) per month.

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

                                             LUMINEX CORPORATION

/s/ A. Sidney Alpert                         By /s/ Mark Chandler
-------------------------------              -----------------------------------
A. Sidney Alpert                                Mark B. Chandler
                                                President and CEO<PAGE>

                                                                   EXHIBIT 10.12

STANDARD COMMERCIAL LEASE AGREEMENT            Approximately 5,906 gross sq. ft.
                                               --------------------------------
    BUILDING) 79                               12212 Technology Blvd., Suite K
                                               --------------------------------
                                               Austin, Texas 78727
                                               --------------------------------
                                               (McNeil #4)

                                Lease Agreement

     THIS LEASE AGREEMENT, made and entered into by and between AEtna Life
Insurance Company hereinafter referred to as "Landlord" and Mark Chandler,
Individually hereinafter referred to as "Tenant";

                                  W I T N E S S E T H:

   1. Premises and Term. In consideration of the obligation of Tenant to pay
rent as herein provided, and in consideration of the other terms, provisions and
covenants hereof, Landlord hereby demises and leases to Tenant, and Tenant
hereby accepts and leases from Landlord certain premises situated within the
County of Travis, State of Texas, more particularly described an Exhibit "A"
attached hereto and incorporated herein by reference, together with all rights,
privileges, easements, appurtenances and immunities belonging to or in any way
pertaining to the premises and together with the buildings and other
improvements situated upon said premises (said real property, buildings and
improvements hereinafter referred to as the "premises").

   TO HAVE AND TO HOLD the same for a term commencing on November 1, 1989 and
ending 55 months thereafter. Tenant acknowledges that it has inspected and
accepts the premises, and specifically the buildings and improvements comprising
the same, in their present condition as suitable for the purpose for which the
premises are leased. Taking of possession by Tenant shall be deemed conclusively
to establish that said buildings and other improvements are in good and
satisfactory condition as of when possession was taken. Tenant further
acknowledges that no representations as to the repair of the premises nor
premises to alter, remodel or improve the premises have been made by Landlord,
unless such are expressly set forth in this lease. If this lease is executed
before the premises become vacant or otherwise available and ready for
occupancy, or if any present tenant or occupant of the premises holds over, and
Landlord cannot acquire possession of the premises prior to the date above
recited as the commencement date of this lease, Landlord shall not be deemed to
be in default hereunder, and Tenant agrees to accept possession of the premises
at such time as Landlord is able to tender the same, which date shall
thenceforth be deemed the "commencement date"; and Landlord hereby waives
payment of rent covering any period prior to the tendering of possession to
Tenant hereunder. After the commencement date Tenant shall, upon demand, execute
and deliver to Landlord a letter of acceptance of delivery of the premises.

   2. Base Rent and Security Deposit.

   A. Tenant agrees to pay to Landlord rent for the premises, in advance,
without demand, deduction or set off, for the entire term hereof at the rate of
see "Rental Rate" paragraph on attached Addendum Dollars ($________) per month.
One such monthly installment shall be due and payable on the date hereof and a
like monthly installment shall be due and payable or before the first day of
each calendar month succeeding the commencement date recited above during the
hereby demised term, except that the rental payment for any fractional calendar
month at the commencement or end of the lease period shall be prorated.

   B. In addition, Tenant agrees to deposit with Landlord on the date hereof the
sum of Two Thousand Nine Hundred Fifty-Three and No/Dollars ($2,953.00), which
sum shall be held by Landlord, without obligation for interest, as security for
the performance of Tenant's covenants and obligations under this lease, it being
expressly understood and agreed that such deposit is not an advance rental
deposit or a measure of Landlord's damages in case of Tenant's default. Upon the
occurrence of any event of default by Tenant, Landlord may, from time to time,
without prejudice to any other remedy provided herein or provided by law, use
such fund to the extent necessary to make good any arrears of rent or other
payments due hereunder, and any other damage, injury, expense or liability
caused by such event of default; and Tenant shall pay to Landlord on demand the
amount so applied in order to restore the security deposit to its original
amount. Although the security deposit shall be deemed the property of Landlord,
any remaining balance of such deposit shall be returned by Landlord to Tenant at
such time after termination of this lease that all of Tenant's obligations under
this lease have been fulfilled.

   3. Use. The demised premises shall be used only for the purpose of receiving,
storing, shipping and selling (other than retail) products, materials and
merchandise made and/or distributed by Tenant and for such other lawful purposes
as may be incidental thereto. Outside storage, including without limitation,
trucks and other vehicles, is prohibited without Landlord's prior written
consent. Tenant shall at its own cost and expense obtain any and all licenses
and permits necessary for any such use. Tenant shall comply with all
governmental laws, ordinances and regulations applicable to the use of the
premises, and shall promptly comply with all governmental orders and directives
for the correction, prevention and abatement of nuisances in or upon, or
connected with, the premises, all at Tenant's sole expense. Tenant shall not
permit any objectionable or unpleasant odors, smoke, dust, gas, noise or
vibrations to emanate from the premises, nor take any other action which would
constitute a nuisance or would disturb or endanger any other tenants of the
building in which the premises are situated or unreasonably interfere with their
use of their respective premises. Without Landlord's prior written consent,
Tenant shall not receive, store or otherwise handle any product, material or
merchandise which is explosive or highly inflammable. Tenant will not permit the
premises to be used for any purpose or in any manner (including without
limitation any method of storage) which would render the insurance thereon void
or the insurance risk more hazardous or cause the State Board of Insurance or
other insurance authority to disallow any sprinkler credits.

   4. Taxes.

   A. Landlord agrees to pay before they become delinquent all taxes,
assessments and governmental charges of any kind and nature whatsoever
(hereinafter collectively referred to as "taxes") lawfully levied or assessed
against the building and the grounds, parking areas, driveways and alleys around
the building; provided, however, that the maximum amount of taxes to be paid by
Landlord hereunder during any one real estate tax year shall be -0-. Tenant
shall pay prorata share of all real estate taxes. If in any real estate tax year
during the term hereof or any renewal or extension the taxes levied or assessed
against the building and the grounds, parking areas, driveways and alleys
around the building during such tax year shall exceed the sum set forth in the
proceeding sentence, Tenant shall pay to Landlord as additional rental, upon
demand, the amount of such excess. In the event any such amount is not paid
within twenty (20) days after the date of Landlord's invoice to Tenant, the
unpaid amount shall bear interest at the rate of ten percent (10%) per annum
from the date of such invoice until payment by Tenant.

   B. In the event the premises constitute a portion of a multiple occupancy
building, Tenant agrees to pay to Landlord, as additional rental, upon demand,
the amount of Tenant's "proportionate share" of the excess taxes referred to in
Paragraph A above.  Tenant's "proportionate share", as used in this lease, shall
mean a fraction, the numerator of which is the space contained in the premises
and the denominator of which is the entire space contained within the building.

   C. If at any time during the term of this lease, the present method of
taxation shall be charged so that in lieu of the whole or any part of any taxes,
assessments or governmental charges levied, assessed or imposed on real estate
and the improvements thereon, there shall be levied, assessed or imposed on
Landlord a capital levy or other tax directly on the rents received therefrom
and/or a franchise tax, assessment, levy or charge measured by or based in
whole or in part, upon such rents for the present or any future building or
buildings on the premises, then all such taxes, assessments, levies, or charges,
or the part thereof so, measured or based, shall be deemed to be included within
the term "taxes" for the purpose hereof. Landlord tax statement with respect to
the premises shall be made available for inspection by Tenant.

   D. The Landlord shall have the right to employ a tax consulting firm to
attempt to assure a fair tax burden on the building and grounds within the
applicable taxing jurisdiction, Tenant shall pay to Landlord upon demand, from
time to time, as additional rent, the amount of Tenant's "proportionate share"
(as defined in subparagraph 4(B) above) of the cost of such service.

   E. Any payment to be made pursuant to this Paragraph 4 with respect to the
real estate tax year in which this lease commences or terminates shall be
prorated.

   5. Landlord's Repairs. Landlord shall at his expense maintain only the roof,
foundation and the structural soundness of the exterior walls of the building in
good repair, reasonable wear and tear excepted. Tenant shall repair and pay for
any damage caused by the negligence of Tenant, or Tenant's employees, agents or
invitees, or caused by Tenant's default hereunder.  The term "walls" as used
herein shall not include windows, glass and plate glass, doors, and special
store fronts and office entrys. Tenant shall immediately give Landlord written
notice of defect or need for repairs after which Landlord shall have twenty (20)
days to repair same or cure such defect or show evidence of intent to repair
same or cure defect within a reasonable period of time. Landlord's liability
with respect to any defects, repairs or maintenance for which Landlord is
responsible under any of the provisions of this lease, shall be limited to the
cost of such repairs or maintenance or the curing of such defect.

   6. Tenant's Repairs

   A. Tenant shall at its own cost and expense keep and maintain all parts of
the premises (except those for which Landlord is expressly responsible under the
terms of this lease) in good condition, promptly making all necessary repairs
and replacements, including but on limited to windows, glass and plate glass,
doors, any special office entry, interior walls and finish work, floors and
floor covering, downspouts, heating and air conditioning systems, dock boards,
truck doors, dock bumpers, paving, plumbing work and fixtures, termite and pest
extermination, regular removal of trash and debris, regular mowing of any grass,
trimming, weed removal and general landscape maintenance. Tenant shall not be
obligated to repair any damage caused by fire, tornado or other casualty covered
by the insurance to be maintained by Landlord pursuant to subparagraph 12(A)
below, except that Tenant shall be obligated to repair all wind damage to glass
except with respect to tornado or hurricane damage.

   B. Tenant shall not damage any demising wall or disturb the integrity and
support provided by any demising wall and shall, at its sole cost and expense
promptly repair any damage or injury to any demising wall caused by Tenant or
its employees, agents or invitees.

   C. In the event the premises constitute a portion of a multiple occupancy
building, Tenant and its employees, customers and licensees shall have the
exclusive right to use the parking areas, if any, as may be designated by
Landlord in writing, subject to such reasonable rule
<PAGE>

and regulations as Landlord may from time to time prescribe and subject to
rights of ingress and egress of other tenants. Landlord shall not be responsible
for enforcing Tenant's exclusive parking rights against any third parties.
Further, in multiple occupancy buildings, Landlord reserves the right to perform
the paving and landscape maintenance, exterior painting and common sewage line
plumbing which are otherwise Tenant's obligations under subparagraph A above,
and Tenant shall, in lieu of the obligations set forth under subparagraph A
above with respect to such items, be liable for its proportionate share (as
defined in subparagraph 4(B) above) of the cost and expense of the care for the
grounds around the building, including but not limited to, the mowing of grass,
care of shrubs, general landscaping, maintenance of parking areas, driveways and
alleys, exterior repainting and common sewage line plumbing; provided, however,
that Landlord shall have the right to require Tenant to pay such other
reasonable proportion of said mowing, shrub care and general landscaping costs
as may be determined by Landlord in its sole discretion; and further provided
that if Tenant or any other particular tenant of the building can be clearly
identified as being responsible for obstructions or stoppage of the common
sanitary sewage line, then Tenant, if Tenant is responsible, or such other
responsible tenant, shall pay the entire cost thereof, with thirty (30) days
written notice as additional rent, Tenant shall pay when due
its share, determined as aforesaid, of such costs and expenses along with the
other tenants of the building to Landlord upon demand, as additional rent, for
the amount of its share as aforesaid of such costs and expenses in the event
Landlord elects to perform or cause to be performed such work.

   E.  Tenant shall, at its own cost and expense, enter into a regularly
scheduled preventive maintenance/service contract with a maintenance contractor
for servicing all hot water, heating and air conditioning systems and equipment
within the premises. The maintenance contractor and the contract must be
approved by Landlord. The service contract must include all services suggested
by the equipment manufacturer within the operation/maintenance manual and must
become effective (and a copy thereof delivered to Landlord) with thirty (30)
days of the date Tenant takes possession of the premises.

  7.   Alterations. Tenant shall not make any alterations, additions or
improvements to the premises (including but not limited to roof and wall
penetrations) without the prior written consent of Landlord. Tenant may, without
the consent of Landlord, but at its own cost and expense and in good workmanlike
manner erect such shelves, bins, machinery, and trade fixtures as it may deem
advisable, without altering the basic character of the building or improvements
and without overloading or damaging such building or improvements, and in each
case complying with all applicable governmental laws, ordinances, regulations
and other requirements. All alterations, additions, improvements, and partitions
erected by Tenant shall be and remain the property of Tenant during the term of
this lease and Tenant shall, unless Landlord otherwise elects as hereinafter
provided, remove all alterations, additions, improvements and partitions erected
by Tenant and paid for by Tenant and restore the premises to their original
condition by the date of termination of this lease or upon earlier vacating of
the premises; provided, however, that if Landlord so elects prior to termination
of this lease or upon earlier vacating of premises, such alterations, additions,
improvements, and partitions shall become the property of Landlord as of the
date of termination of this lease or upon earlier vacating of the premises and
shall be delivered up to the Landlord with the premises. All shelves, bins,
machinery and trade fixtures installed by Tenant may be removed by Tenant prior
to the termination of this lease if Tenant so elects, and shall be removed by
the date of termination of this lease or upon earlier vacating of the premises
if required by Landlord; upon any such removal Tenant shall restore the
premises to their original condition. All such removals and restoration shall be
accomplished in a good workmanlike manner so as not to damage the primary
structure or structural qualities of the buildings and other improvements
situated on the premises.

   8.  Signs. Tenant shall have the right to install signs upon the premises
only when first approved in writing by Landlord and subject to any applicable
governmental laws, ordinances, regulations and other requirements. Tenant shall
remove all such signs by the termination of this lease. Such installations and
removals shall be made in such manner as to avoid injury or defacement of the
building and other improvements, and Tenant shall repair any injury or
defacement, including without limitation discoloration, caused by such
installation and/or removal.

   9.  Inspection. Landlord and Landlord's agents and representatives shall have
the right to enter and inspect the premises at any reasonable time during
business hours, for the purpose of ascertaining the condition of the premises or
in order to make such repairs as may be required or permitted to be made by
Landlord under the terms of this lease.  During the period that is six (6)
months prior to the end of the term hereof, Landlord and Landlord's agents and
representatives shall have the right to enter the premises at any reasonable
time during business hours for the purpose of showing the premises and shall
have the right to erect on the premises a suitable sign indicating the premises
are available.  Tenant shall give written notice to Landlord at least thirty
(30) days prior to vacating the premises and shall arrange to meet with Landlord
for a joint inspection of the premises prior to vacating.  In the event of
Tenant's failure to give such notice or arrange such joint inspection,
Landlord's inspection at or after Tenant's vacating the premises shall be
conclusively deemed correct for purposes of determining Tenant's reasonable
responsibility for repairs and restoration.

   10. Utilities.  Landlord agrees to provide at its cost water, electricity and
telephone service connections into the premises; but Tenant shall pay for all
water, gas, heat, light, power, telephone, sewer, sprinkler charges and other
utilities and services used on or from the premises, together with any taxes,
penalties, surcharges of the like pertaining thereto and any maintenance charges
for utilities and shall furnish all electric light bulbs and tubes. If any such
services are not separately metered to Tenant, Tenant shall pay a reasonable
proportion as determined by Landlord of all charges jointly metered with other
premises. Landlord shall in no event be liable for any interruption or failure
of utility services on the premises.

   11. Assignment and Subletting.  Tenant shall not have the right to assign
this lease or to sublet the whole or any part of the premises without the prior
written consent of Landlord which consent shall not be unreasonable withheld.
Notwithstanding any permitted assignment or subletting, Tenant shall at all
times remain directly, primarily and fully responsible and liable for the
payment of the rent herein specified and for compliance with all of its other
obligations under the terms, provisions and covenants of this lease. Upon the
occurrence of an "event of default" as hereinafter defined, if the premises or
any part thereof are then assigned or sublet, Landlord, in addition to any other
remedies herein provided, or provided by law, may at its option collect directly
from such assignee or subtenant all rents becoming due to Tenant under such
assignment or sublease and apply such rent against any sums due to Landlord from
Tenant hereunder, and no such collection shall be construed to constitute a
novation or a release of Tenant from the further performance of Tenant's
obligations hereunder.

   12. Fire and Casualty Damage.
   A.  Landlord agrees to maintain standard fire and extended coverage insurance
covering the building of which the premises are a part in an amount not less
than 80% (or such greater percentage as may be necessary to comply with the
provisions of any co-insurance clauses of the policy) of the "replacement cost"
thereof as such term is defined in the Replacement Cost Endorsement to be
attached thereto, insuring against the perils of Fire, Lightning, and Extended
Coverage, such coverages and endorsements to be as defined, provided and limited
in the standard bureau forms prescribed by the insurance regulatory authority
for the State in which the premises are situated for use by insurance companies
admitted in such state for the writing of such insurance on risks located within
such state.  Subject to the provisions of subparagraphs 12(C), 12(D), and 12(E)
below, such insurance shall be for the sole benefit of Landlord and under its
sole control.  If during the second full lease year after the commencement date
of this lease, or during any subsequent year of the primary term or any renewal
or extension, Landlord's cost of maintaining such insurance shall exceed
Landlord's cost of maintaining such insurance for the first full lease year of
the term hereof, Tenant agrees to pay to Landlord, as additional rent, the
amount of such excess (or in the event the premises constitute a portion of a
multiple occupancy building, Tenant's full proportionate share (as defined in
subparagraph 4(B) above) of such excess).  Said payments shall be made to
Landlord within ten (10) days after presentation to Tenant of Landlord's
statement setting forth the amount due. Any payment to be made pursuant to this
subparagraph A with respect to the year in which this lease commences or
terminates shall bear the same ratio to the payment which would be required to
be made for the full year as the part of such year covered by the term of this
lease bears to a full year.

   B.  If the buildings situated upon the premises should be damaged or
destroyed by fire, tornado, or other casualty, Tenant shall give immediate
written notice thereof to Landlord.

   C.  If the buildings situated upon the premises should be totally destroyed
by fire, tornado, or other casualty, or if they should be so damaged thereby
that rebuilding or repairs cannot in Landlord's estimation be completed within
one hundred fifty (150) days after the date upon which Landlord is notified by
Tenant of such damage, this lease shall terminate and the rent shall be abated
during the unexpired portion of this lease, effective upon the date of the
occurrence of such damage.

   D.  If the buildings situated upon the premises should be damaged by any
peril covered by the insurance to be provided by Landlord under subparagraph
12(A) above, but only to such extent that rebuilding or repairs can in
Landlord's estimation be completed within one hundred fifty (150) days after the
date upon which the Landlord is notified by Tenant of such damage, this lease
shall not terminate, and Landlord shall at its sole cost and expense thereupon
proceed with reasonable diligence to rebuild and repair such buildings to
substantially the condition in which they existed prior to such damage, except
that Landlord shall not be required to rebuild, repair or replace any part of
the partitions, fixtures, additions and other improvements which may have been
placed in, on or about the premises by Tenant. If the premises are untentantable
in whole or in part following such damage, the rent payable hereunder during the
period in which the are untentantable shall be reduced to such extent as may be
fair and reasonable under all the circumstances. In the event that Landlord
should fail to complete such repairs and rebuilding within one hundred fifty
(150) days after the date upon which Landlord is notified by Tenant of such
damage, Tenant may at its option terminate this lease by delivering written
notice of termination to Landlord as Tenant's exclusive remedy, whereupon all
rights and obligations hereunder shall cease and terminate.

   E.  Notwithstanding anything herein to the contrary, in the event the holder
of any indebtedness secured by a mortgage or deed of trust covering the premises
requires that the insurance proceeds be applied to such indebtedness, then
Landlord shall have the right to terminate this lease by delivering written
notice of termination to Tenant within fifteen (15) days after such requirement
is made by any such holder, whereupon all rights and obligations hereunder shall
cease and terminate.

   F.  Each of Landlord and Tenant hereby releases the other from any loss or
damage to property caused by fire or any other perils insured through or under
them by way of subrogation or otherwise for any loss or damage to property
caused by fire or any other perils insured in policies of insurance covering
such property, even if such loss or damage shall have been caused by the fault
or negligence of the other party, or anyone for whom such party may be
responsible; provided, however, that this release shall be applicable and in
force and effect only with respect to loss or damage occurring during such times
as the releasor's policies shall contain a clause or endorsement to the effect
that any such release shall not adversely affect or impair said policies or
prejudice the right of the releasor to recover thereunder and then only to the
extent of the insurance proceeds payable under such policies. Each of the
Landlord and Tenant agrees that it will request its insurance carriers to
include in its policies such a clause or endorsement. If extra cost shall be
charged therefor, each party shall advise the other thereof and of the amount of
the extra cost, and the other party, at its election, may pay the same, but
shall not be obligated to do so.

   13. Liability.  Landlord shall not be liable to Tenant or Tenant's employees,
agents, patrons or visitors, or to any other person whomsoever, for any injury
to person or damage to property on or about the premises, resulting from and/or
caused in part or whole by the negligence or misconduct of Tenant, its agents,
servants or employees, or of any person entering upon the premises, or caused by
the buildings and improvements located on the premises becoming our of repair,
or caused by leakage of gas, oil, water or steam or by electricity emanating
from the premises, or due to any cause whatsoever, and Tenant hereby covenants
and agrees that it will at all times indemnify and hold safe and harmless the
property, the Landlord (including without limitation the trustee and
beneficiaries if Landlord is a trust), Landlord's
<PAGE>

agents and employees from any loss, liability, claims, suits, costs, expenses,
including without limitation attorney's fees and damages, both real and alleged,
arising out of such damage or injury; except injury to persons or damage to
property the sole cause of which is negligence of Landlord or the failure of
Landlord to repair any part of the premises which Landlord is obligated to
repair and maintain hereunder within a reasonable time after the receipt of
written notice from Tenant of needed repairs. Tenant shall procure and maintain
throughout the term of this lease a policy or policies of insurance, at its sole
cost and expense, insuring both Landlord and Tenant against all claims, demands
or actions arising out of or in connection with: (i) the premises; (ii) the
condition of the premises; (iii) Tenant's operations in and maintenance and use
of the premises; and (iv) Tenant's liability assumed under this lease, the
limits of such policy or policies to be in the amount of not less than $300,000
per occurrence in respect of injury to persons (including death), and in the
amount of not less than $50,000 per occurrence in respect of property damage or
destruction, including loss of use thereof. All such policies shall be procured
by Tenant from responsible insurance companies satisfactory to Landlord.
Certified copies of such policies, together with receipt evidencing payment of
premiums therefor, shall be delivered to Landlord prior to the commencement date
of this lease. Not less than fifteen (15) days prior to the expiration date of
any such policies, certified copies of the renewals thereof (bearing notations
evidencing the payment of renewal premiums) shall be delivered to Landlord. Such
policies shall further provide that not less than thirty (30) days written
notice shall be given to Landlord before such policy may be cancelled or changed
to reduce insurance provided thereby.

   14. Condemnation.

   A.  If the whole or any substantial part of the premises should he taken for
any public or quasi-public use under governmental law, ordinance or regulation,
or by right of eminent domain, or by private purchase in lieu thereof and the
taking would prevent or materially interfere with the use of the premises or the
normal operation of the company for the purpose which they are being used, this
lease shall terminate and the rent shall be abated during the unexpired portion
of this lease, effective When the physical taking of said premises shall occur.

   B.  If part of the promises shall be taken for any public or quad-public use
under any governmental law, ordinance or regulation, or by right of eminent
domain, or by private purchase in lieu thereof, and this lease is not terminated
as provided in the subparagraph above, this lease shall not terminate but the
rent payable hereunder during the unexpired portion of this lease shall be
reduced to such extent as may be fair and reasonable under all of the
circumstances.

   C.  In the event of any such taking or private purchase in lieu thereof,
Landlord and Tenant shall each be entitled to receive and retain such separate
awards and/or portion of lump sum awards as may be allocated to their respective
interests in any condemnation proceedings.

   15. Holding Over.  Tenant will, at the termination of this lease by lapse of
time or otherwise, yield up immediate possession to Landlord. If Landlord agrees
in writing that Tenant may hold over after the expiration or termination of this
lease, unless the parties hereto otherwise agree in writing on the terms of such
holding over, the hold over tenancy shall be subject to termination by Landlord
at any time upon not less than five (5) days advance written notice, or by
Tenant at any time upon not less than thirty (30) days advance written notice,
and all of the other terms and provisions of this lease shall be applicable
during that period, except that Tenant shall pay Landlord from time to time upon
demand, as rental for the period of any hold over, an amount equal to one and
one-half (1 1/2) the rent in effect on the termination date, computed on a daily
basis for each day of the hold over period. No holding over by Tenant, whether
with or without consent of Landlord, shall operate to extend this lease except
as otherwise expressly provided. The preceding provisions of this paragraph 15
shall not be construed as Landlord's consent for Tenant to hold over.

   16. Quiet Enjoyment.  Landlord covenants that it now has, or will acquire
before Tenant takes possession of the premises, good title to the premises, free
and clear of all liens and encumbrances, excepting only the lien for current
taxes not yet due, such mortgage or mortgages as are permitted by the terms of
this lease, zoning ordinances, and other building and fire ordinances and
governmental regulations relating to the use of such property, and easements,
restrictions and other conditions of record. In the event this lease is a
sublease, then Tenant agrees to take the premises subject to the provisions of
the prior leases. Landlord represents and warrants that it has full right and
authority to enter into this lease and that Tenant, upon paying the rental
herein set forth and performing its other covenants and agreements herein set
forth, shall peaceably and quietly have, hold and enjoy the premises for the
term hereof without hindrance or molestation from Landlord, subject to the terms
and provisions of this lease.

   17. Events of Default. The following events shall be deemed to be events of
default by Tenant under this lease:

       (a) Tenant shall fail to pay any installment of the rent herein reserved
   when due, or any payment with respect to taxes hereunder when due, or any
   other payment or reimbursement to Landlord required herein when due, and such
   failure shall continue for a period of five (5) days from the date such
   payment was due.

       (b) Tenant shall become insolvent, or shall make a transfer in fraud of
   creditors, or shall make an assignment for the benefit of creditors.

       (c) Tenant shall file a petition under any section or chapter of the
   National Bankruptcy Act, as amended, or under any similar law or statute of
   the United States or any State thereof; or Tenant shall be adjudged bankrupt
   or insolvent in proceedings filed against Tenant thereunder.

       (d) A receiver or trustee shall be appointed for all or substantially all
   of the assets of Tenant

       (e) Tenant shall desert or vacate any substantial portion of the
   promises.

       (f) Tenant shall fail to comply with any term, provision or covenant of
   this lease (other than the foregoing in this paragraph 17), and shall not
   cure such failure within thirty (30) days after written notice thereof to
   Tenant.

   18. Remedies. Upon the occurrence of any such event of default described in
paragraph 17 hereof, Landlord shall have the option to pursue any one or more of
the following remedies without notice or demand whatsoever:

       (a) Terminate this lease, in which event Tenant shall immediately
   surrender the premises to Landlord, and if Tenant fails so to do, Landlord
   may, without prejudice to any other remedy which it may have for possession
   or arrearages in rent, enter upon and take possession of the premises, and
   expel or remove Tenant and any other person who may be occupying such
   premises or any part thereof, and Tenant agrees to pay to Landlord on demand
   the amount of all loss and damage which Landlord may suffer by reason of such
   termination, whether through inability to relet the premises on satisfactory
   terms or otherwise.

       (b) Enter upon and take possession of the premises and expel or remove
   Tenant and any other person who may be occupying such premises or any part
   thereof, by force if necessary, without being liable for prosecution or any
   claim for damages therefor, and relet the premises and receive the rent
   therefor; and Tenant agrees to pay to the Landlord on demand any deficiency
   that may arise by reason of such reletting. In the event Landlord is
   successful in reletting the premises at a rental in excess of that agreed to
   be paid by Tenant pursuant to the terms of this lease, Landlord and Tenant
   each mutually agree that Tenant shall not be entitled, under any
   circumstances, to such excess rental, and Tenant does hereby specifically
   waive any claim to such excess rental.

       (c) Enter upon premises, and do whatever Tenant is obligated to do under
   the terms of this lease; and Tenant agrees to reimburse Landlord on demand
   for any expenses which Landlord may incur in thus effecting compliance with
   Tenant's obligations under this lease.

In the event Tenant fails to pay any installment of rent hereunder as and when
such installment is due, to help defray the additional cost to Landlord for
processing such late payments Tenant shall pay to Landlord on demand a late
charge in an amount equal to five (5%) of such installment; and the failure to
pay such amount within twenty (20) days after demand therefor shall be an event
of default hereunder.  The provision for such late charge shall be in addition
to all of Landlord's other rights and remedies hereunder or at law and shall not
be construed as liquidated damage or as limiting Landlord's remedies in any
manner.

   Pursuit of any of the foregoing remedies shall not preclude pursuit of any of
the other remedies herein provided or any other remedies provided by law, nor
shall pursuit of any remedy herein provided constitute a forfeiture or waiver of
any rent due to Landlord hereunder or of any damages accruing  to Landlord by
reason of the violation of any of the terms, provisions and covenants herein
contained. No act or thing done by the Landlord or its agents during the term
hereby granted shall be deemed a termination of this lease or an acceptance of
the surrender of the premises, and no agreement to terminate this lease or
accept a surrender of said premises shall be valid unless in writing signed by
Landlord. No waiver by Landlord of any violation or breach of any of the terms,
provisions and covenants herein contained be deemed or construed to constitute a
waiver of any other violation or breach of any of the terms, provisions and
covenants herein contained. Landlord's acceptance of the payment of rental or
other payments hereunder after the occurrence of an event of default shall not
be construed as a waiver of such default, unless Landlord so notifies Tenant in
writing. Forbearance by Landlord to enforce one or more of the remedies herein
provided upon an event of default shall not be deemed or construed to constitute
a waiver of such default or of Landlord's right to enforce any such remedies
with respect to such default or subsequent default. If, on account of any breach
or default by Tenant in Tenant's obligations under the terms and conditions of
this lease, it shall become necessary or appropriate for Landlord to employ or
consult with an attorney concerning or to enforce or defend any of Landlord's
rights or remedies hereunder, Tenant agrees to pay any reasonable attorneys fees
so incurred. This clause shall be mutually applied to Landlord or Tenant.

   19. Landlord's Lien.  In addition to any statutory lien for rent in
Landlord's favor, Landlord shall have and Tenant hereby grant to Landlord a
continuing security interest for all rentals and other sums of money becoming
due hereunder from Tenant, upon all goods, wares, equipment, fixtures,
furniture, inventory, accounts, contract rights, chattel paper and other
personal property of Tenant situated on the premises, and such property shall
not be removed therefrom without the consent of Landlord until all arrearages in
rent as well as any and all other sums of money then due to Landlord hereunder
shall first have been paid and discharged. In the event of a default under this
lease, Landlord shall have, in addition to any other remedies provided herein or
by law, all rights and remedies under the Uniform Commercial Code, including
without limitation the right to sell the property described in this Paragraph 19
at public or private sale upon ten (10) days notice to Tenant. Tenant hereby
agrees to execute such financing statements and other instruments necessary or
desirable in Landlord's discretion to perfect the security interest hereby
created. Any statutory lien for rent is not hereby waived, the express
contractual lien herein granted being in addition and supplementary thereto.

   20. Mortgages.  Tenant accepts this lease subject and subordinate to any
mortgage(s) and/or deed(s) of trust now or at any time here after constituting a
lien or charge upon the premises or the improvements situated thereon, provided,
however, that if the mortgagee trustee or holder of any such mortgage or deed of
trust elects to have Tenant's interest in this lease superior to such lien,
whether this lease was executed before or after said mortgage or deed of trust.
Tenant shall at any time hereafter on demand execute any instruments, releases
or other documents which may be required by any mortgagee for the purpose of
subjecting and subordinating this lease to the lien of any such mortgage.

   21. Landlord's Default.  In the event Landlord should become in default in
any payments due on any such mortgage described in Paragraph 20, hereof or in
the payment of taxes or any other items which might become a lien upon the
premises and which Tenant is not obligated to pay under the terms and provisions
of this lease, Tenant is authorized and empowered after giving Landlord five (5)
days prior written notice of such default and Landlord's failure to cure such
default, to pay any such items for and on behalf of Landlord, and the amount of
any item so paid by Tenant for or on behalf of Landlord, together with any
interest or penalty required to be paid in connection therewith, shall
<PAGE>

be payable on demand by Landlord to Tenant; provided, however, that Tenant shall
not be authorized and empowered to make any payment under the terms of this
Paragraph 21 unless the item paid shall be superior to Tenant's interest
hereunder. In the event Tenant pays any mortgage debt in full, in accordance
with this paragraph, it shall, at its election, be entitled to the mortgage
security by assignment or subrogation.

   22. Mechanic's Liens. Tenant shall have no authority, express or implied, to
create or place any lien or encumbrance of any kind or nature whatsoever upon,
or in any manner to bind, the interest of Landlord in the premises or to charge
the rentals payable hereunder for any claim in favor of any person dealing with
Tenant, including those who may furnish materials or perform labor for any
construction or repairs, and each such claim shall affect and each such lien
shall attach to, If at all, only the leasehold interest granted to Tenant by
this instrument. Tenant covenants and agrees that it will pay or cause to be
paid all sums legally due and payable by it on account of any labor performed
or materials furnished in connection with any work performed on the premises on
which any lien is or can be validly and legally asserted against its leasehold
interest in the premises or the improvements thereon and that it will save and
hold Landlord harmless from any and all loss, cost or expense based on or
arising out of asserted claims or liens against the leasehold estate or against
the right, title and interest of the Landlord in the premises or under the terms
of this lease.

   23. Notices. Each provision of this instrument or of any applicable
governmental laws, ordinances, regulations and other requirements with reference
to the sending, mailing or delivery of any notice or the making of any payment
by Landlord to Tenant or with reference to the sending, mailing or delivery of
any notice or the making of any payment by Tenant to Landlord shall be deemed to
be complied with when and if the following steps are taken:

       (a) All rent and other payments required to be made by Tenant to Landlord
   hereunder shall be payable to Landlord at the address hereinbelow set forth
   or at such other address as Landlord may specify from time to time by written
   notice delivered in accordance herewith. Tenant's obligation to pay rent and
   any other amounts to Landlord under the terms of this lease shall not be
   deemed satisfied until such rent and other amounts have been actually
   received by Landlord.

       (b) All payments required to be made by Landlord to Tenant hereunder
    shall be payable to Tenant at the address hereinbelow set forth, or at such
    other address within the continental United States as Tenant may specify
    from time to time by written notice delivered in accordance herewith.

       (c) Any notice or document required or permitted to be delivered
    hereafter shall be deemed to be delivered whether actually received or not
    when deposited in the United States Mail, postage prepaid, Certified or
    Registered Mail, addressed to the parties hereto at the respective addresses
    set out below, or at such other address as they have theretofore specified
    by written notice delivered in accordance herewith.

                 LANDLORD:                             TENANT:

       AEtna Life Insurance Company           Mark Chandler, Individually
   ------------------------------------    ----------------------------------
       c/o Trammell Crow Company              12212 Technology Blvd., Suite K
   ------------------------------------    ----------------------------------
       301 Congress Avenue, Suite 1300        Austin, Texas 78727
   ------------------------------------    ----------------------------------
       Austin, Texas 78701
   ------------------------------------
      (P.O. Box 2176, Austin, TX 78768)

If and when included within the term "Landlord" as used in this instrument,
there are more than one person, firm or corporation, all shall jointly arrange
among themselves for their joint execution of such a notice specifying some
individual at some specific address for the receipt of notices and payments to
Landlord if and when included within the term "Tenant", as used in this
instrument, there are more than one person, firm or corporation, all shall
jointly arrange among themselves for their joint execution of such a notice
specifying some individual at some specific address within the continental
United States for the receipt of notices and payments to Tenant. All parties
included within the terms "Landlord" and "Tenant", respectively, shall be bound
by notices given in accordance with the provisions of this paragraph to the same
effect as if each had received such notice.

   24. Miscellaneous.

   A.  Words of any gender used in this lease shall be held and construed to
include any other gender, and words in the singular number shall be held to
include the plural, unless the context otherwise requires.

   B.  The terms, provisions and covenants and conditions contained in this
lease shall apply to, inure to the benefit of, and be binding upon, the parties
hereto and upon their respective heirs, legal representative, successors and
permitted assigns, except as otherwise herein expressly provided. Landlord shall
have the right to assign any of its rights and obligations under this lease.
Each party agrees to furnish to the other, promptly upon demand a corporate
resolution, proof of due authorization by partners, or other appropriate
documentation evidencing the due authorization, of such party to enter into this
lease.

   C.  The captions inserted in this lease are for convenience only and in no
way define, limit or otherwise describe the scope or intent of this lease, or
any provision hereof, or in any way affect the interpretation of this lease.

   D.  Tenant agrees from time to time within test (10) days after request of
Landlord, to deliver to Landlord, or Landlord's designee an estoppel certificate
stating that this lease is in full force and effect, the date to which rent has
been paid, the unexpired term of this lease and such other matters pertaining to
this lease as may be requested by Landlord. It is understood and agreed that
Tenant's obligation to furnish such estoppel certificates in a timely fashion is
a material inducement for Landlord's execution of this lease.

   E.  This lease may not be altered, changed or amended except by an instrument
in writing signed by both parties hereto.

   F.  All obligations of Tenant hereunder not fully performed as of the
expiration or earlier termination of the term of this lease shall survive the
expiration or earlier termination of the term hereof including without
limitation all payment obligations with respect to taxes and insurance and all
obligations concerning the condition of the premises. Upon this expiration or
earlier termination of the term hereof. and prior to Tenant vacating the
premises, Tenant shall pay to Landlord any amount reasonably estimated by
Landlord as necessary to put the premises, including without limitation all
heating and air conditioning systems and equipment therein, In good condition
and repair. Tenant shall also, prior to vacating the premises, pay to Landlord
the amount, as estimated by Landlord, of Tenant's obligation hereunder for real
estate taxes and insurance premiums for the year in which the lease expires or
terminates. All such amounts shall be used and held by Landlord for payment of
such obligations of Tenant hereunder, with Tenant being liable for any
additional costs therefor upon demand by Landlord, or with any excess to be
returned to Tenant after all such obligations have been determined and
satisfied, as the case may be. Any security deposit held by Landlord shall be
credited against the amount payable by Tenant under this Paragraph 24(F).

   G.  If any clause or provision of this lease is Illegal, invalid or
unenforceable under present or future laws effective during the term of this
lease, then and in that event, it is the intention of the parties hereto that
the remainder of the lease shall not be affected thereby, and it is also the
intention of the parties to this lease that in lieu of each clause or provision
of this lease that is illegal, invalid or unenforceable, there be added as a
part of this lease contract a clause or provision as similar in terms to such
illegal, invalid or unenforceable clause of provision as may be possible and be
legal, valid and enforceable.

   H.  Because the premises are on the open market and are presently being
shown, this lease shall be treated as an offer with the premises being subject
to prior lease and such offer subject to withdrawal or non-acceptance by
Landlord or to other use of the premises without notice, and this lease shall
not be valid or binding unless and until accepted by Landlord in writing and a
fully executed copy delivered to both parties hereto.

   I.  All references in this lease to "the data hereof" or similar references
shall be deemed to refer to the last date, in point of time, on which all
parties hereto have executed this lease.

   25. Additional Provisions.  See Addendum and Exhibits "A" and "B" attached
hereto and made a part thereof.

   EXECUTED BY LANDLORD, this        day of             , 19 .

Attest/Witness;                       Aetna Life Insurance Company
                                      ----------------------------------------

/s/ [ILLEGIBLE]                       By /s/ [ILLEGIBLE]
----------------------------------       -------------------------------------

Title: Leasing Agent                  Title: Assistant Vice President
      ----------------------------           ---------------------------------

   EXECUTED BY TENANT, this 1 day of August, 1989

Attest/Witness

                                      ________________________________________

/s/ Mark Chandler                     By /s/ Mark Chandler
----------------------------------      --------------------------------------

Title:____________________________    ________________________________________
<PAGE>

                     ADDENDUM TO LEASE AGREEMENT BETWEEN
                   AETNA LIFE INSURANCE COMPANY, AS LANDLORD
                        AND MARK CHANDLER, INDIVIDUALLY

RENTAL RATE
-----------

The monthly base rental shall be paid according to the following schedule:

   Months 1 - 6 @ $2,000.00 gross (common area maintenance and taxes will not be
   due during this period.)

   Months 7 - 55 @ $2,953.00 triple net (common area maintenance and taxes will
   be due during this period.)

CONSTRUCTION AND WORKMANSHIP WARRANTIES
---------------------------------------

The Tenant shall be assigned the entire rights of Landlord in all warranties
provided by the subcontractors relating to the finish-out construction of the
demised premises.  This assignment of rights and warranties shall coincide with
the term of the lease.  If for any reason the Tenant no longer occupies the
premises before the expiration of any warranties, then the assignment of the
warranties shall revert back to the Landlord.  Landlord shall be responsible for
contracting and supervising the construction of the improvements to be
constructed in the demised space, as described in Exhibit "B" attached hereto.
Landlord warrants that HVAC has been serviced and is in good working order for a
period of 90 days following occupancy.

PARKING
-------

The Tenant shall have the right to use fifteen (15) parking spaces of the total
spaces provided for the building on a non-exclusive basis during the term of the
lease.  These spaces shall be provided at no cost to the Tenant.  If no such
event shall the Tenant be entitled to paint, mark or otherwise identify any such
spaces for its exclusive use.  Tenant shall prevent its employees from parking
on the streets adjacent to the premises and use its best effort to prevent all
other invitees from parking on such streets.

COMMON AREA MAINTENANCE
-----------------------

In addition to the obligations and responsibilities of the Tenant documented in
Paragraph 6 "Tenant Repairs" of the lease, Tenant shall be responsible for its
proportionate share of all costs involving the non-structural maintenance of (1)
the exterior of the building, (2) the building and park landscaping, (3) the
parking lots and driveways, (4) interior and exterior sprinkler systems and any
other miscellaneous costs of the common area maintenance of the building and
park or park security.

ESCROW DEPOSIT
--------------

During each month of the term of this lease, Tenant shall make a monthly escrow
deposit with Landlord equal to 1/12 of its proportionate share of the taxes,
common area maintenance charges and common utility charges which will be due and
payable for that particular year and which are Tenant's obligations pursuant to
Paragraphs 4, 6, and 10 of the Lease, respectively.  Tenant authorizes Landlord
to use the funds so deposited with Landlord to pay such costs.  Within ninety
(90) days after execution of this lease by both parties, Landlord shall estimate
all such costs for the year in question.  The initial monthly escrow payment
required above shall be based upon Tenant's proportionate share of the estimated
costs, and the monthly escrow payments are subject to increase or decrease as
determined by Landlord to reflect an accurate monthly escrow of Tenant's
estimated proportionate share of all such costs.  The escrow payment account of
Tenant shall be reconciled annually.  If the Tenant's total escrow payments are
less than Tenant's actual proportionate share of all such costs, Tenant shall
pay Landlord upon demand the difference; if the total escrow payments of Tenant
are more than Tenant's actual proportionate share of all such costs, Landlord
shall retain such excess and credit it to Tenant's next accruing escrow account
payments.

Tenant shall escrow estimated common area maintenance and property tax charges
during months 7 through 55.
<PAGE>

                     ADDENDUM TO LEASE AGREEMENT BETWEEN
                AETNA LIFE INSURANCE COMPANY, AS LANDLORD AND
                     MARK CHANDLER, INDIVIDUALLY, AS TENANT
                                PAGE TWO OF TWO

FINISH OUT
----------

Finish out will be constructed according to Tenant and Landlord approved plans
and specifications to be attached at a later date.  In no event shall Tenant
finish out exceed $45,000.00.

SIGNAGE
-------

Landlord will pay for building standard sign or pay for moving and installing
Tenant's existing sign.

RENEWAL OPTION
--------------

Tenant shall have the right and option to renew this lease for one (1)
additional five (5) year term by delivering written notice thereof to Landlord
at lease One Hundred and eighty (180) days prior to the expiration date of the
lease term, provided that at the time of such notice and at the end of the lease
term, Tenant is not in default hereunder.  Upon the delivery of said notice and
subject to the conditions set forth in the preceding sentence, this lease shall
be extended upon the same terms, covenants and conditions as provided in this
lease, except that the rental payable during said extended term shall be at the
prevailing market rental rate for space of comparable size, quality and location
at the commencement of such extended term.  If a conflict arises in the
determination of such a Fair Market Value rental rate, a three-member committee,
selected from the Austin Board of Realtors, shall determine the Fair Market
Value rental rate.  The first two members of such committee shall be selected by
Landlord and Tenant respectively, which two members shall select the third.  In
no event shall the rate decrease below the rate Tenant is currently paying.

Landlord agrees to subordinate its contractual lien hereunder to any purchase
money or working capital line of credit financing.

Tenant must notify Landlord in writing upon each and every "secured party"
desiring to perfect their purchase money or working capital line of credit
financing.
<PAGE>

                                  EXHIBIT "A"

LEGAL DESCRIPTION:  Lot 10 of the McNeil Commercial Subdivision, Section Two, a
-----------------
                    subdivision in Travis County, Texas

LOCAL ADDRESS:      12212-K Technology Blvd.
--------------
                    Austin, Texas 78759

                              [Map Appears Here]
<PAGE>

                                  EXHIBIT "B"

The tenant finish improvements will be constructed in accordance with the
"Industrial Standards and Specifications" dated February 1986, unless noted
otherwise on the construction drawings relating to the leased premises.

Actual construction plans will be accepted and agreed to as a separate document.
<PAGE>

                   FIRST AMENDMENT TO LEASE AGREEMENT BETWEEN
                AETNA LIFE INSURANCE COMPANY, AS LANDLORD AND
                    MARK CHANDLER, INDIVIDUALLY, AS TENANT
                                DATED: 10/4/89

              This Amendment, shall attach to and form a part of
              the Lease Agreement and shall supersede and amend
              such Lease as follows:

Toxic Waste
-----------

Tenant covenants not to introduce any form of hazardous or toxic materials, as
defined by the U.S. Environmental Protection Agency onto the Premises without:
a) first obtaining Landlords written consent: and b) complying with all
applicable Federal, State and local laws or ordinances pertaining to the
transportation, storage, use or disposal of such material, including but not
limited to obtaining proper permits.

If Tenant's transportation, storage, use or disposal of hazardous or toxic
materials the Premises results in: 1) contamination of the soil or surface or
ground water: or 2) loss or damage to person(s) or property, then Tenant
agrees to respond in accordance with the following paragraph.

Tenant agrees: (i) to notify Landlord immediately of any contamination, claim of
contamination, loss or damage; (ii) after consultation and approval by Landlord,
to clean up the contamination in full compliance with all applicable statutes,
regulations and standard, and (iii) to indemnify, claims, suits, causes of
action, costs and fees, including attorney's fees, arising from or connected
with any such contamination, claim on contamination, loss or damage. This
provision shall survive termination of this lease.

WITNESS:                                     AETNA LIFE INSURANCE COMPANY:

_________________________________            /s/ [ILLEGIBLE]
                                             ----------------------------------

WITNESS:                                     MARK CHANDLER, INDIVIDUALLY

/s/ [ILLEGIBLE]                              /s/ Mark Chandler
----------------------------------           -----------------------------------
<PAGE>

                  SECOND AMENDMENT TO LEASE AGREEMENT BETWEEN
                 AETNA LIFE INSURANCE COMPANY, AS LANDLORD AND
                     MARK CHANDLER, INDIVIDUALLY, AS TENANT

        To be attached to and form a part of Lease made the 1st day of
        August, 1989, (which together with any amendments, modifications
        and extensions thereof, is hereafter called the Lease), between,
        Landlord and Tenant, covering a total of 2,625 squaw feet and
        located at 12212 Technology Boulevard, Suite K, Austin, Texas.

     WITNESSETH, THAT

     WHEREAS, Tenant needs additional space for its business purposes and
Landlord has available an area adjacent hereto.

     NOW, THEREFORE, in consideration of the premises, Landlord and Tenant
covenant and agree as follows:

     1.   Effective January 1, 1992 through end of Term, the demised promises
stall contain, in addition to the approximately 5,906 square feet originally
demised, an additional area hereinafter called the "new space", containing
approximately 2,625 square feet immediately adjacent thereto (see Exhibit "A"
attached hereto), thus making the aggregate area of the demised premises
approximately 8,531 square feet.

     2.   Landlord shall provide Tenant with a tenant finish allowance of
$10,000.00. All improvements must comply with Landlord's Standards and
                                              ------------------------
Specifications for Office/Warehouse Buildings.
---------------------------------------------

     3.   Effective January 1, 1992, the monthly rental for the entire 8,531
square feet shall be $4,265.50 Triple Net, payable on the first day of each
month during the balance of the term.

          Except as herein and hereby modified and amended the Agreement of
Lease shall remain in full force and effect and all the terms, provisions,
covenants and conditions thereof are hereby ratified and confirmed.

DATE AS OF THE 10 DAY OF DECEMBER, 1991

WITNESS:                                AETNA LIFE INSURANCE COMPANY:

/s/ [ILLEGIBLE]                              /s/ [ILLEGIBLE]
----------------------------------           -----------------------------------
                                             BY:
                                             TITLE: Director

WITNESS:                                     MARK CHANDLER INDIVIDUALLY:

/s/ [ILLEGIBLE]                              BY: /s/ Mark Chandler
----------------------------------              --------------------------------

                                             TITLE: President
                                                   -----------------------------
<PAGE>

                                  EXHIBIT "A"

BUILDING:                McNeil #4

LEGAL DESCRIPTION:       Lot 10, McNeil Road Commercial Subdivision,
                         Section 2

ADDRESS:                 12212 Technology Boulevard, suites J & K,
                         Austin, Texas 78727

                                        NEW SPACE    ORIGINAL SPACE
                                        2,625 s.f.     5,906 s.f.

                              [MAP APPEARS HERE]
<PAGE>

                  THIRD AMENDMENT TO LEASE AGREEMENT BETWEEN
                AETNA LIFE INSURANCE COMPANY, AS LANDLORD, AND
                    MARK CHANDLER, INDIVIDUALLY, AS TENANT

        To be attached to and form a part of Lease made the 1st day of
        August, 1989 (which together with any amendments, modifications
        and extensions thereof, is hereinafter called the Lease), between
        Landlord and Tenant, covering a total of 8,531 square feet and
        located at 12212 Technology Boulevard, Austin, Texas, known as
        McNeil 4..

     1.   WITNESSETH that the Lease is hereby extended and renewed for a further
term of Sixty (60) months to commence on the 1st day of June, 1994, on condition
that Landlord and Tenant comply with all terms, covenants and conditions
contained in the Lease, and the monthly base rental shall be Four Thousand Nine
Hundred Forty Seven and 98/100 Dollars ($4,947.98) plus property taxes, common
area maintenance, and insurance as provided in the Lease. The Tenant shall
accept the space in its current "as is" condition.

     2.   Landlord shall provide a tenant finish allowance of $2.00 per square
foot ($17,062.00) to be applied. toward interior improvements. Tenant shall be
responsible for the amount of tenant improvements in excess of the finish-out
allowance of $2.00 per square foot. All improvements must comply with Trammell
Crow Company's standard specifications (see Standards and Specifications for
                                            --------------------------------
Office/Warehouse Buildings) and all applicable governmental regulations. Prior
--------------------------
to beginning construction of any such improvements, Tenant shall submit
architectural drawings of the proposed improvements to Landlord and shall obtain
Landlord's written consent to begin construction.

     3.   The Landlord will provide the Tenant with an HVAC Certificate of
Inspection within thirty (30) days of the commencement of the renewal term. If
the HVAC units require repair or replacement, the Landlord will do so at its
cost.

     Except as herein and hereby modified and amended the Agreement of Lease
shall remain in full force and effect and all the terms, provisions, covenants
and conditions thereof an hereby ratified and confirmed.

DATED AS OF THE 29 DAY OF APRIL, 1994.

WITNESS:                                     AETNA LIFE INSURANCE COMPANY

___________________________                  By: /s/ [ILLEGIBLE]
                                                -----------------------------

                                             Title: Director
                                                   --------------------------

WITNESS:                                     MARK CHANDLER, INDIVIDUALLY:

[ILLEGIBLE]
---------------------------                  By: Mark Chandler
                                                -----------------------------

                                             Title:__________________________
<PAGE>

                                  EXHIBIT "A"

BUILDING:                     McNeil #4

LEGAL DESCRIPTION:            Lot 10, McNeil Road Commercial Subdivision,
                              Section 2

ADDRESS:                      12212 Technology Boulevard
                              Austin, Texas 78727

                              [MAP APPEARS HERE]
<PAGE>

                  FOURTH AMENDMENT TO LEASE AGREEMENT BETWEEN
                 AETNA LIFE INSURANCE COMPANY, AS LANDLORD AND
                    MARK CHANDLER, INDIVIDUALLY, AS TENANT

     To be attached to and form a part of Lease made the 1st day of
     August, 1989 (which together with any amendments, modifications
     and extensions thereof, is hereinafter called the Lease), between
     Landlord and Tenant, covering a total of 8,531 square feet and
     located at 12212 Technology Boulevard, Suites J and K, Austin,
     Texas, known as McNeil #4.

WITNESSETH That the Lease is hereby amended as follows:

1.   The Lease shall be extended and renewed for a further term of four (4)
months to commence on the 1st day of June, 1999, on condition that Landlord and
Tenant comply with all terms, covenants and conditions contained in the Lease,
and the monthly base rental shall be as follows. The Tenant shall accept the
space in its current "as is" condition.

2.   WHEREAS, Tenant needs additional space for its business purposes and
Landlord has available an area adjacent hereto, effective on the commencement
date, the demised premises shall contain, in addition to the approximately 8,531
square feet originally demised, an additional area, hereinafter called the "new
space," containing approximately 4,206 square feet adjacent thereto (see Exhibit
"A" attached hereto), thus making the aggregate area of the demised promises
approximately 12,737 square feet. Tenant shall accept the "new space" in its
current "as is" condition and all improvements must comply with Landlord's
Standards and Specifications for Office/Warehouse Buildings.

     The commencement due for the new space is defined as thirty (30) days
following existing tenant's vacation of the "new space" and their completion of
responsibilities outlined in Paragraph 4 of this document.

     3.   The Monthly Rental shall be as follows:

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------------
                          MONTHLY BASE         MONTHLY BASE        MONTHLY BASE
                       RENTAL PSF EXISTING    RENTAL EXISTING     RENTAL PSF NEW         MONTHLY BASE      TOTAL MONTHLY
TERM                     SPACE (8531 SF)          SPACE           SPACE (4,206 SF)     RENTAL NEW SPACE      BASE RENTAL
--------------------------------------------------------------------------------------------------------------------------
<S>                    <C>                    <C>                 <C>                  <C>                 <C>
Commencement -
 5/30/99                     $0.58                $4,947.98            $0.65              $2,733.90           $7,681.88
--------------------------------------------------------------------------------------------------------------------------
6/1/99 - 9/30/99             $0.58                $4,974.98            $0.65              $2,733.90           $7,681.88
--------------------------------------------------------------------------------------------------------------------------
</TABLE>

These amounts shall be in addition to property taxes, common area maintenance,
and insurance as provided in the Lease.

     4.   Previous Tenant or Landlord shall be responsible for servicing and
repairing, if necessary, the HVAC system, by a mutually acceptable, licensed
contractor, cleaning the "new space" to broom clean condition and for building
an opening in the demising wall between the "existing space" and the "new space"
prior to occupancy of the "new space" by Tenant.

     5.   Paragraph 9.B.(i) of the Lease Agreement is hereby amended to name the
Management Company as an additional insured on all Tenant's Liability Insurance
Policies in connection with this Lease (except for the workers' compensation
policy as stated in Paragraph 9.B.(i)).

     6.   Except as herein and hereby modified and amended the Agreement of
Lease shall remain in full force and effect and all the terms, provisions,
covenants and conditions thereof are hereby ratified and confirmed.

DATED AS OF THE 7 DAY OF JUNE, 1996.

WITNESS:                      LANDLORD:
                              AETNA LIFE INSURANCE COMPANY
                              BY: Alleges Realty Investors, LLC its Agent
                              and Investment Advisor

/s/ Kim House                 /s/ [ILLEGIBLE]
-----------------------       --------------------------------------
                              Printed Name: [ILLEGIBLE]
                                           -------------------------
                              Title:        Vice President
                                           -------------------------

WITNESS:                      TENANT:
                              MARK CHANDLER, INDIVIDUALLY

Kim House                     /s/ Mark Chandler
-----------------------       --------------------------------------
                              Printed Name: Mark Chandler
                                           -------------------------
                              Title:       _________________________

<PAGE>

                                  EXHIBIT "A"

BUILDING:                McNeil #4

LEGAL DESCRIPTION:       Lot 10, McNeil Road Commercial Subdivision,
                         Section 2

ADDRESS:                 12212 Technology Boulevard
                         Austin, Texas 78727

                              [MAP APPEARS HERE]
<PAGE>

                  FIFTH AMENDMENT TO LEASE AGREEMENT BETWEEN
                AETNA LIFE INSURANCE COMPANY, AS LANDLORD, AND
                    MARK CHANDLER, INDIVIDUALLY, AS TENANT

          To be attached to and form a part of Lease made the 1/st/
          day of August, 1989 (which together with any amendments,
          modifications and extensions thereof, is hereinafter called
          the Lease), between Landlord and Tenant, covering a total of
          12,737 square feet and located at 12212 Technology Boulevard,
          Suites I, J and K, Austin, Texas, known as McNeil #4

WITNESSETH that the Lease is hereby amended as follows:

     1.   The Lease shall be extended and renewed (see Exhibit "A") for a
further term. of thirty (30) months to commence on the 1/st/ day of October
1999, on condition that Landlord and Tenant comply with all terms, covenants and
conditions contained in the Lease. The Tenant shall accept the space in its
current "as is" condition.

     2.   WHEREAS, Tenant needs, additional space for its business purposes and
Landlord has available an area nearby effective on Commencement Date, the
demised premises shall contain, in addition to the approximately 12,737 square
feet originally demised ("original space"), and additional area, hereinafter
called the "new space", containing approximately 20,122 square feet located at
12212 Technology Boulevard, Suite 200 (known as McNeil #5) (see Exhibit "B")
attached hereto, thus making the aggregate area of the premises approximately
32,859 square feet.

The Commencement Date for the new space is defined as forty five (45) days
following existing tenant's vacation of the "new space" and the completion of
responsibilities outlined in Paragraph 4 of this document.

     3.   Monthly Rental shall be as follows:

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------------------------
                              MONTHLY BASE           MONTHLY BASE       MONTHLY BASE
                           RENTAL PSF EXISTING     RENTAL EXISTING         PSF NEW           MONTHLY BASE       TOTAL MONTHLY
TERM                        SPACE (12,737 SF)            SPACE         SPACE (20,122 SF)     RENTAL NEW SPACE     BASE RENTAL
------------------------------------------------------------------------------------------------------------------------------
<S>                        <C>                     <C>                 <C>                   <C>                <C>
Commencement-9/30/99           $0.6031153              $7,681.88             $0.75            $15,091.50           $22,773.38
------------------------------------------------------------------------------------------------------------------------------
10/1/99 - 3/31/02              $     0.75              $9,552.75             $0.75            $15,091.50           $24,644.25
------------------------------------------------------------------------------------------------------------------------------
</TABLE>

These amounts shall be in addition to property taxes, common area maintenance,
and insurance as provided in the Lease.  Tenant shall be obligated to pay its
proportionate share of management fees for the new space as of the Commencement
Date.  As of October 1, 1999, Tenant shall pay its proportionate share of
management fees on the original space.

     4.   Previous tenant or Landlord shall be responsible for servicing and
repairing, if necessary, the HVAC system by a mutually acceptable, licensed
contractor and cleaning the "new space" to broom clean condition, including but
not limited to, removal of trash and previous Tenant's equipment.

     5.   With one hundred eighty (180) days prior written notice and so long as
                                                                  --------------
Tenant is not in default under the terms of this Lease, Tenant shall have the
------------------------------------------------------
right to cancel the Lease after April 1, 2001. Should Tenant elect to exercise
such option, Tenant shall pay to Landlord a Termination Fee of Ninety Six
Thousand Two Hundred Five and 25/100 Dollars ($96,205.25). Fifty percent (50%)
of such Termination Fee is payable at the time such notice is served. The
remaining fifty percent (50%) is payable a the time of lease termination.

     6.   Landlord shall provide a tenant finish allowance of $40,224.00 to be
applied toward interior improvements. Tenant shall bear the entire cost of any
interior improvements to be installed by Landlord in the premises in excess of
the finish-out allowance of $40,224.00 and shall pay for such excess over the
allowance as hereinafter provided.
<PAGE>

In no event shall credit be given to Tenant for any allowance not utilized. All
improvements must comply with Trammell Crow Company's standard specifications
(see Standards and Specifications for Office/Warehouse Buildings) and all
     -----------------------------------------------------------
applicable governmental regulations. Prior to beginning construction of any such
improvements, Tenant shall submit architectural drawings of the proposed
improvement to Landlord and shall obtain Landlord's written consent to begin
construction. Notwithstanding any provision herein to the contrary, Tenant will
utilize a general contractor, approved by Landlord, to construct the interior
improvements in the new space. Tenant will have the right to access, occupy and
conduct business in the new space up to, but not exceeding, forty five (45) days
prior to the Commencement Date without any rent obligation. Tenant will
construct the interior improvements in the new space with reasonable diligence,
but need not finish them prior to the Commencement Date; such improvements may
be constructed while Tenant is occupying and conducting business in the new
space. Tenant may draw the allowance from Landlord from time to time as
construction bills come due.

     7.   Witnesseth that the Lease expressly refers to Tenant as Mark Chandler,
Individually.  From and after the date hereof, the Tenant shall be Luminex
Corporation and not Mark Chandler, Individually.  The Lease and all related
documents are hereby amended such that all references to "Tenant" or "Mark
Chandler, Individually", will translate to mean "Luminex Corporation".

     8.   Tenant shall have the right and option to renew this Lease for one (1)
additional thirty-six (36) month term by delivering written notice thereof at
least one hundred eighty (180) days prior to the expiration date of the lease
term, provided that at the time of such notice and at the end of the lease term,
Tenant is not in default hereunder.  Upon the delivery of said notice and
subject to the conditions set forth in the preceding sentence, this Lease shall
be extended upon the same terms, covenants and conditions as provided in this
Lease, except that the rental payable during said extended term shall be the
prevailing market rental rate for space of comparable size, quality and location
at the commencement of such extended term (the "Market Rate").  The right and
option shall apply to the initial lease term only.  In the event Landlord and
Tenant are unable to agree upon the Market Rate, Landlord and Tenant shall each
promptly appoint a real estate broker who is licensed by the Texas Real Estate
Commission (TREC) and active in the Austin industrial market, to assist in the
determination of the Market Rate, and the two brokers shall appoint a third
broker who is also licensed by the Texas Real Estate Commission and active in
the Austin industrial market.  The determination of the Market Rate by agreement
of any two of such three brokers shall thereafter be payable until further
adjusted.  Landlord and Tenant agree to use all reasonable diligence to cause
their appointed brokers to perform in good faith and in a timely manner in order
to make the determination of the Market Rate on or before the date on which the
Market Rate is to become effective.  In the event the brokers to not make such
determination in a timely manner, this Lease shall nevertheless continue in full
force and effect until such determination is made, and the rental for such
period shall be payable at the rate otherwise payable hereunder.  Upon the
determination of the Market Rate, the payment of the Market Rate shall commence
on the first day of the month following the date of such determination, and in
addition to such monthly installment of rental, Tenant shall pay to Landlord in
the increase in rental payment hereunder, if any, applicable to the period from
the date on which the Market Rate was scheduled to become effective to the
payment of the first installment at the Market Rate.  Landlord and Tenant shall
each bear the cost and fees of their respective brokers and shall share equally
the cost of the third broker, if needed.

     9.   Tenant, at its own cost and expense, shall enter into a regularly
scheduled preventative maintenance/service contract with a maintenance
contractor approved by Landlord for servicing all hot water, heating and air
conditioning systems and equipment within the Premises. The service contract
must include the replacement of filters on a regular basis and all services
suggested by the equipment manufacturer in its operations/maintenance manual and
must become effective within thirty (30) days of the date Tenant takes
possession of the Premises. Provided that
<PAGE>

Tenant maintains such service contract and is not in default under the terms of
this Lease, Landlord shall be responsible for any repairs or replacements
necessary to maintain the HVAC equipment in the new space for a period of sixty
(60) days following the Commencement Date.

     10.  Tenant shall have the nonexclusive right to utilize no more than
fifty-six (56) parking spaces at the new space and no more than thirty-nine (39)
parking spaces at the original space.

     11.  Tenant's "proportionate share" of McNeil #4 is 35.93%.  Tenant's
proportionate share of McNeil #5 is 45.34%.

     12.  Subject to Landlord's written approval of the installation process and
procedure, Tenant, at its expense, shall have the right to install
telecommunication lines connecting the new space and original space.

     13.  Tenant shall not use, and shall not permit any subtenant licensee,
concessionaire, employee, agent or invitee (hereinafter collectively "Tenant's
Representatives") to use, any portion of the Premises or Building, for the
placement, storage, manufacture, disposal or handling of any hazardous materials
(hereinafter defined) unless Tenant complies with all applicable environmental
laws (federal, state and local), including, but not limited to those for
obtaining proper permits.  In the event Tenant or Tenant's Representatives
desire to use or place hazardous materials on the Premises it shall notify
Landlord in writing thirty (30) days prior to such proposed use or placement,
and provide the names of the hazardous materials, procedures to insure
compliance with the applicable environmental laws and such other information as
Landlord may reasonable request.

     In the event Tenant or Tenant's Representatives places, releases, or
discovers any hazardous materials on the Premises or Building in violation of
applicable environmental laws, Tenant shall immediately notify Landlord of such
fact in writing within twenty-four (24) hours of the placement, release or
discovery. Tenant shall not attempt any removal, abatement or remediation of
those hazardous materials on the Premises in violation of applicable
environmental laws, without obtaining the additional written consent of
Landlord, which consent may be specifically conditioned on Landlord's right to
approve the scope, timing and techniques of any such work and the appointment of
all contractors, engineers, inspectors and consultants in connection with any
such work. Tenant shall be responsible for the cost of any removal, abatement
and remediation work of any hazardous materials placed, stored, manufactured,
disposed of or handled by Tenant or Tenant's Representatives on the Premises or
any other portion of the Building and for the cost of any removal abatement or
remediation of any hazardous materials which might be disturbed or released as a
result of any remodeling or construction in the Premises by Tenant or Tenant's
Representatives. Such cost shall include, without limitation, the cost of any
supervision by Landlord, its employees or agents, in connection with such work.
Tenant shall comply with all environmental laws in connection with any such
removal.

     Tenant shall indemnify Landlord, its shareholders, directors, officers,
employees and agents and hold them harmless, from and against any loss, damage
(including, without limitation, a loss in value of the Building or damages due
to restrictions on marketing contaminated space), cost, liability, expense
(including reasonable attorney's fees and expenses and court costs) arising out
of the placement, storage, use, manufacture, disposal, handling, removal,
abatement or remediation of any hazardous materials by Tenant or Tenant's
Representatives on the Premises or Building, or any removal, abatement or
remediation of any hazardous materials required hereunder to be performed or
paid for by Tenant, with respect to any portion of the Premises or the Building,
or arising out of any breach by Tenant of its obligations under this paragraph.

     The term "hazardous materials" as used herein shall mean (i) any "hazardous
waste" as defined by the Resource Conservation and Recovery Act of 1976 (42
U.S.C. Section 6901 et seq.), as amended from time to time, and regulations
promulgated thereunder; (ii) any "hazardous substance" as defined by the
Comprehensive Environmental Response, Compensation and Liability Act of 1980 (42
U.S.C. Section 9601, et seq.), as amended from time to time, and regulations
promulgated thereunder; (iii) asbestos or polychlorinated biphenyls; (iv) any
substance the presence of which on the Building or on the Premises is prohibited
or regulated by any federal, state or local law, regulation, code or rule; and
(v) any other substance
<PAGE>

which requires special handling or notification of any federal, state, or local
governmental entity in its collection, storage, treatment, or disposal.

     14.  This Lease shall be subordinate to any deed of trust, mortgage, of
other security instrument (a "Mortgage"), of any ground lease, master lease, or
primary lease (a "Primary Lease"). that now or hereafter covers all or any part
of the Premises (the mortgagee under any Mortgage or the lessor under any
Primary Lease is referred to herein as "Landlord's Mortgagee"), including any
modifications, renewals or extensions of such Mortgage or Primary Lease,
provided that it is a condition to the Subordination of this lease that the
Landlord's Mortgagee execute and deliver to Tenant a non-disturbance and
attornment agreement, in recordable form, whereby such Landlord's Mortgagee
agrees that neither this Lease nor Tenant's right to possession will be
terminated so long as Tenant is not in default under this Lease (provided
Landlord's Mortgagee, or successor thereto, maintains its rights to terminate
under other provisions of the Lease, e.g., for a casualty). Notwithstanding the
foregoing, Tenant agrees that any such Landlord's Mortgagee shall have the right
at any time to subordinate such Mortgage or Primary Lease to this lease on such
terms and subject to such conditions as Landlord's Mortgagee may deem
appropriate in its discretion. Tenant agrees upon demand to execute such further
instruments subordinating this Lease or attorning to the Landlord's Mortgagee as
Landlord may request, provided such contains non-disturbance provisions as noted
above and such other provisions which do not affect The substantive provisions
of this Lease. In the event that Tenant should fail to execute any subordination
or other agreement required by this paragraph, within twenty (20) days of
written request, it shall constitute an Event of Default, without further notice
required of Landlord.

     Except as herein and hereby modified and amended the Agreement of Lease
shall remain in full force and effect and all the terms, provisions, covenants
and conditions thereof are hereby ratified and confirmed.

DATED AS OF THE 21/st/ DAY OF DECEMBER, 1998.

WITNESS:                           AETNA LIFE INSURANCE COMPANY:

                                   By:    Allegis Realty Investors LLC,
                                          Its Investment Advisor sad Agent

/s/ [ILLEGIBLE]                    /s/ [ILLEGIBLE]
   -------------------------          -----------------------------------

                                   By:    [ILLEGIBLE]
                                      -----------------------------------

                                   Title: Senior Vice President
                                         --------------------------------

WITNESS:                           LUMINEX CORPORATION:

                                   /s/ Mark Chandler
                                   --------------------------------------

                                   By     MARK CHANDLER
                                     ------------------------------------

                                   Title: CHAIRMAN & CEO
                                         --------------------------------
<PAGE>

                                  EXHIBIT "A"

BUILDING:                   McNeil #4

LEGAL DESCRIPTION:          Lot 10, McNeil Road Commercial Subdivision,
                            Section 2

ADDRESS:                    12212 Technology Boulevard
                            Austin, Texas 78727

                              [MAP APPEARS HERE]
<PAGE>

                                  EXHIBIT "B"

BUILDING:                   McNeil #5

LEGAL DESCRIPTION:          Lot 10, McNeil Road Commercial Subdivision,
                            Section 2

ADDRESS:                    12112 Technology Boulevard
                            Austin, Texas 78727

                              [MAP APPEARS HERE]

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