<PAGE>

                                                                  EXHIBIT 10.2



                               LUMINEX CORPORATION

                           RESTRICTED STOCK AGREEMENT

         THIS RESTRICTED STOCK AGREEMENT (this "Agreement") dated as of May 15,
2004, is entered into between Luminex Corporation, a Delaware corporation (the
"Company"), and Patrick J. Balthrop (the "Stockholder"). The Company and the
Stockholder agree as follows:

         1. DEFINITIONS.

                  1.1 The terms "Cause", "Change in Control", "Termination Other
Than For Cause" and "Termination by Reason of Incapacity" shall have the
respective meanings set forth in that certain Employment Agreement dated to be
effective as of May 15, 2004 between Company and Stockholder (the "Employment
Agreement").

                  1.2 "Person" means any individual, corporation, partnership,
limited liability company, joint venture, association, joint stock company,
trust, unincorporated organization or government or any agency or political
subdivision thereof.

         2. ACQUISITION OF RESTRICTED STOCK. Concurrently with the execution and
delivery hereof, the Company has issued to the Stockholder 200,000 shares of the
Company's common stock ("Common Stock") pursuant to the Company's 2000 Long-Term
Incentive Plan (the "Plan"). The Company and the Stockholder have determined
that it would be in their best interests to impose certain rights and
obligations upon the Company, the Stockholder and his legal representatives, as
the case may be, with respect to such 200,000 shares of Common Stock (as
adjusted for stock splits, dividends and the like, the "Shares").

         3. RESTRICTION PERIOD. During the period (the "Restriction Period")
commencing as of the date of this Agreement (the "Commencement Date") and ending
on the fifth anniversary of the date of this Agreement, the Shares shall be
subject to the restrictions described in Section 4 of this Agreement (the
"Restrictions"). The Shares subject to the Restrictions at any given time are
called the "Restricted Shares."

         4. RESTRICTIONS. The Restricted Shares shall be represented by one or
more stock certificates registered in the name of the Stockholder. The
Stockholder shall have the right to receive dividends on the Restricted Shares,
to vote the Restricted Shares and to enjoy all other stockholder rights with
respect thereto, except that (i) the Stockholder shall not be entitled to
possession of the stock certificate representing the Restricted Shares, (ii) the
Company shall retain custody of the stock certificate(s) representing the
Restricted Shares, (iii) the Stockholder may not, other than as permitted under
Section 9.2, sell, transfer, pledge, exchange, hypothecate or otherwise dispose
of the Restricted Shares and (iv) the Restricted Shares are subject to potential
forfeiture as provided in Section 5 of this Agreement.

         5. FORFEITURE. Any Restricted Shares (and all voting and other rights
associated with such Restricted Shares) shall be automatically forever forfeited
to the Company on the fifth




                                       1
<PAGE>

anniversary of the date of this Agreement to the extent that the Restrictions
with respect to such Restricted Shares have not lapsed prior to the fifth
anniversary of the date of this Agreement. In addition, any Restricted Shares
(and all voting and other rights associated with such Restricted Shares) shall
be forever forfeited (to the extent that the Restrictions with respect to such
Restricted Shares have not previously lapsed) in the event (i) such Restricted
Shares are transferred by operation of law to any Person other than the Company
or in accordance with Section 9.2 for any reason (including without limitation
the bankruptcy of the Stockholder and seizure and sale by legal process), or
(ii) the Stockholder's employment with the Company is terminated prior to the
end of the Restriction Period. The Company shall not be obligated to pay the
Stockholder any amount for the forfeiture of any Restricted Shares. The
Stockholder shall be entitled to retain all Shares to which the Restrictions
have ceased to apply.

         6. LAPSE OF RESTRICTIONS. The restrictions shall lapse only as follows:

                  (a)      With respect to 33,333 Shares, after such time as the
                           daily closing price of the Common Stock as reported
                           on the Nasdaq National Market System has not been
                           less than $20 per share (as proportionately adjusted
                           to reflect any stock splits, stock dividends,
                           like-kind stock distributions, recapitalizations,
                           mergers or similar events concerning the Common
                           Stock) for at least 60 consecutive calendar days;

                  (b)      With respect to 33,333 Shares, after such time as the
                           daily closing price of the Common Stock as reported
                           on the Nasdaq National Market System has not been
                           less than $25 per share (as proportionately adjusted
                           to reflect any stock splits, stock dividends,
                           like-kind stock distributions, recapitalizations,
                           mergers or similar events concerning the Common
                           Stock) for at least 60 consecutive calendar days;

                  (c)      With respect to 66,667 Shares, upon Stockholder
                           meeting reasonable objective written performance
                           criteria relating to the Company's earnings before
                           interest, taxes, depreciation and amortization
                           (EBITDA) established within 120 days after the date
                           of this Agreement by the Board of Directors of the
                           Company or the Compensation Committee thereof (the
                           "Board"). Before establishing such criteria, the
                           Board shall consult with Stockholder and consider any
                           criteria suggested by Stockholder; and

                  (d)      With respect to 66,667 Shares, upon Stockholder
                           meeting reasonable objective written performance
                           criteria relating to the Company's revenues
                           established within 120 days after the date of this
                           Agreement by the Board. Before establishing such
                           criteria, the Board shall consult with Stockholder
                           and consider any criteria suggested by Stockholder.

Notwithstanding the foregoing, however, the Restrictions shall lapse
automatically with respect to all 200,000 Shares (unless earlier forfeited in
accordance with Section 5) upon the consummation of a Change of Control.



                                       2
<PAGE>

         7. RESTRICTIONS ON CORRESPONDING SECURITIES AND ASSETS. Any other
securities or assets (other than ordinary cash dividends) that are received by
the Stockholder with respect to any of the Restricted Shares shall be subject to
the Restrictions to the same extent and for so long as such Restricted Shares to
which such securities or other assets are attributable remain subject to the
Restrictions.

         8. DELIVERY OF CERTIFICATES UPON LAPSE OF RESTRICTIONS. Promptly
following the lapse of the Restrictions as to any of the Shares, the Company
will deliver the stock certificate or certificate representing such Shares with
respect to which the Restrictions have lapsed to the Stockholder or his legal
representative.

         9. CERTAIN RESTRICTIONS ON TRANSFERABILITY OF SHARES BY THE
STOCKHOLDER. The following restrictions shall apply to all Restricted Shares,
whether or not issued or outstanding at the date of this Agreement.

                  9.1 Restriction on Transfers in Violation of the Securities
Act. Notwithstanding any provision to the contrary contained herein, in no event
shall the Stockholder make any disposition of the Shares, including a
disposition by pledge, if such disposition might reasonably be expected to
result in a violation of the Securities Act of 1933, as amended (the "Securities
Act"), or any applicable state's securities laws. Unless the Company agrees
otherwise, the Stockholder shall be required to provide an opinion of counsel
acceptable to the Company with regard to such intended disposition.

                  9.2 Permitted Transfers. The Stockholder may transfer all or
any part of the Shares, to (i) the members of the immediate family of the
Stockholder (including lineal descendants) or one or more trusts or partnerships
for the benefit of the Stockholder and/or members of the immediate family of the
Stockholder (including lineal descendants); or (ii) the estate of the
Stockholder or to any heir, executor, administrator or lineal descendant of the
Stockholder; provided that prior to any such transfer either the Stockholder or
the transferee delivers to the Company a written instrument in accordance with
Section 10 and an opinion of counsel reasonably satisfactory to the Company in
accordance with Section 9.1 to the effect that the transfer is exempt from
registration under the Securities Act. In the event of a transfer under this
Section 9.2, such transferee(s) shall be deemed a Stockholder for purposes of
this Agreement.

         10. ADDITIONAL ISSUANCES. It shall be a condition to the transfer of
any Restricted Shares by the Stockholder to any Person that the recipient of
such Restricted Shares shall become a signatory to this Agreement by executing
an Addendum Agreement in the form and substance satisfactory to the Company.

         11. LEGENDS OF CERTIFICATES. The reverse side of each certificate
reflecting ownership of the Restricted Shares subject to the Restrictions under
Section 4 shall bear the following legends:

                  THE SHARES REPRESENTED HEREBY AND THE SALE, ASSIGNMENT,
                  TRANSFER, GIFT, BEQUEST, PLEDGE OR OTHER DISPOSITION THEREOF
                  ARE SUBJECT TO CERTAIN RESTRICTIONS CONTAINED IN A RESTRICTED
                  STOCK AGREEMENT DATED EFFECTIVE AS OF MAY 15,



                                       3
<PAGE>

                  2004, AMONG THE COMPANY AND THE HOLDER HEREOF. A COPY OF SUCH
                  AGREEMENT AND ALL APPLICABLE AMENDMENTS THERETO WILL BE
                  FURNISHED BY THE COMPANY TO THE HOLDER HEREOF WITHOUT CHARGE
                  UPON WRITTEN REQUEST TO THE COMPANY AT ITS PRINCIPAL PLACE OF
                  BUSINESS OR REGISTERED OFFICE.

                  THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
                  REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND
                  THUS MAY NOT BE OFFERED FOR SALE, SOLD, TRANSFERRED OR
                  OTHERWISE DISPOSED OF, UNLESS THEY ARE REGISTERED UNDER THE
                  SECURITIES ACT OF 1933, AS AMENDED, OR UNLESS AN EXEMPTION
                  FROM SUCH REGISTRATION IS AVAILABLE AND AN OPINION IN FORM AND
                  SUBSTANCE AND FROM COUNSEL SATISFACTORY TO THE COMPANY HAS
                  BEEN RECEIVED BY THE COMPANY.

         12. NOTICES. Any notice required or permitted under this Agreement
shall be in writing and shall be deemed to be delivered (i) upon physical
delivery (if hand delivered); (ii) three business days after deposit in the
United States mail (if mailed), postage prepaid, certified or registered mail,
return receipt requested, addressed as set forth below or (iii) the day such
notice is sent via facsimile as set forth below:

         Company:                 Luminex Corporation
                                  12212 Technology Boulevard
                                  Austin, Texas 78727
                                  Attention: General Counsel
                                  Fax: (512) 219-63295

         Stockholder:             Notices to Stockholder shall be given at the
                                  most recent address of Optionee on the
                                  Company records.

Notice given in any other manner shall be effective when received. The address
for notice may be changed by notice given in accordance with this provision. If
notice is required to be delivered to any party to this Agreement, a copy of
such notice shall be delivered to all other parties to this Agreement.

         13. POWER OF ATTORNEY. The Chairman of the Board of the Company, from
time to time, is hereby appointed the attorney-in-fact, with full power of
substitution of the Stockholder for the sole purpose of carrying out the
provisions of this Agreement and taking any action and executing any instrument
which such attorney-in fact may deem necessary or advisable to accomplish the
purposes hereof, which appointment as attorney-in fact is irrevocable and
coupled with an interest. The Chairman of the Board of the Company, as
attorney-in-fact for the Stockholder may, in the name of the Stockholder, make
and execute all conveyances, assignments and transfers of the Restricted Shares,
and the Stockholder hereby ratifies and confirms all that the Chairman of the



                                       4
<PAGE>


Board of the Company, as said attorney-in-fact, shall do so by virtue hereof,
provided that the foregoing shall be solely for the purpose of carrying out the
provisions of this Agreement. Nevertheless, the Stockholder shall, if so
requested by the Company, execute and deliver to the Company all such
instruments as may, in the reasonable judgment of the Company, be advisable for
the purposes hereof.

         14. WAIVER. No waiver of any provision of this Agreement shall
constitute a waiver of any other provision of this Agreement, nor shall such
waiver constitute a waiver of any subsequent breach of such provision.

         15. BINDING EFFECT. This Agreement shall be binding upon and shall
inure to the benefit of the Stockholder and their heirs, executors,
administrators and legal representatives and upon the Company and its successors
and assigns.

         16. GOVERNING LAW; VENUE. The validity, construction, and enforcement
of this Agreement shall be governed by the laws of the State of Delaware,
without regard for any principles of conflict of laws. Any dispute arising out
of or relating to this Agreement may be brought in a court of competent
jurisdiction located in Austin, Texas, and both of the parties to this Agreement
irrevocably submit to the exclusive jurisdiction of such courts in any such
dispute, waives any objection it may now or hereafter have to venue or to
convenience of forum, agrees that all claims in respect of the dispute shall be
heard and determined only in any such court, and agrees not to bring any dispute
arising out of or relating to this Agreement in any other court. The parties
agree that either or both of them may file a copy of this paragraph with any
court as written evidence of the knowing, voluntary and bargained agreement
among the parties irrevocably to waive any objections to venue or to convenience
of forum. Process in any dispute may be served on any party anywhere in the
world.

         17. SEVERABILITY. If any provision of this Agreement is declared
unenforceable by a court of last resort, such declaration shall not affect the
validity of any other provision of this Agreement.

         18. CONSTRUCTION. The headings contained in this Agreement are for
reference purposes only and shall not affect this Agreement in any manner
whatsoever. Wherever required by the context, any gender shall include any other
gender, the singular shall include the plural, and the plural shall include the
singular.

         19. AMENDMENTS. This Agreement may only be amended or modified by
written agreement of the Company and the Stockholder.

         20. EFFECT OF PLAN AND AUTHORITY OF BOARD. This Agreement and the
Shares granted hereby are subject to the Plan, which is incorporated herein by
reference. The Board is authorized to make all determinations and
interpretations with respect to matters arising under the Plan, this Agreement
and the Shares granted hereunder. Capitalized terms used and not otherwise
defined herein have the respective meanings given them in the Plan, which is
attached hereto and incorporated herein by reference for all purposes.



                                       5
<PAGE>


         THE PARTIES HAVE EXECUTED THIS AGREEMENT EFFECTIVE AS OF THE DATE FIRST
SET FORTH ABOVE.



LUMINEX CORPORATION



By:  /s/ Harriss T. Currie                        /s/ Patrick J. Balthrop
     ---------------------------                  -----------------------------
Name: Harriss T. Currie, its                      Patrick J. Balthrop
      Chief Financial Officer



         The undersigned, the spouse of the Stockholder, hereby joins in the
execution and delivery of this Agreement to evidence her consent and approval
to, and agreement to be bound by, all the terms and provisions hereof.


/s/ Mariterese Balthrop
-----------------------------------





                                       6