<PAGE>
Exhibit 5.1
THOMPSON & KNIGHT L.L.P.
ATTORNEYS AND COUNSELORS
98 SAN JACINTO BLVD., SUITE 1200
AUSTIN, TEXAS 78701
(512) 469-6100
FAX: (512) 469-6180
September 27, 2000
Luminex Corporation
12212 Technology Blvd.
Austin, Texas 78727
Re: Luminex Corporation
Ladies and Gentlemen:
We have acted as counsel for Luminex Corporation, a Delaware corporation
(the "Company"), in connection with the registration under the Securities Act of
1933, as amended (the "Act"), of an aggregate of 2,599,500 shares (the "Shares")
of the common stock, $.001 par value per share (the "Common Stock"), of the
Company consisting of shares issuable pursuant to its 2000 Long-Term Incentive
Plan (the "Plan"). A registration statement on Form S-8 (the "Registration
Statement") covering the issuance and sale of the Shares from time to time upon
their purchase or upon exercise of stock options to be granted under the Plan
under the Act has been filed with the Securities and Exchange Commission (the
"Commission").
In reaching the conclusions expressed in this opinion, we have examined
executed copies of the Registration Statement and all exhibits thereto. We
have also examined and relied upon the original, or copies certified to our
satisfaction, of (i) the Certificate of Incorporation and the Bylaws of the
Company, (ii) minutes and records of the corporate proceedings of the Company
with respect to the issuance of the Shares and related matters, (iii) the Plan
and (iv) such other agreements and instruments relating to the Company as we
have deemed necessary or appropriate for purposes of the opinions hereinafter
expressed. In rendering such opinions, we have made such further investigation
and inquiries relevant to the transactions contemplated by the Registration
Statement as we have deemed necessary to the opinions expressed herein and have
relied, to the extent we deemed reasonable, on certificates and certain other
information provided to us by officers of the Company and public officials as to
matters of fact of which the maker of each such certificate or the person
providing such other information had knowledge. Furthermore, in rendering such
opinions, we have assumed that the signatures on all documents examined by us
are genuine, that all documents and corporate record books submitted to us as
originals are accurate and complete, and that all documents submitted to us as
copies are true, correct and complete copies of the originals thereof.
In issuing the opinions hereinafter expressed, we do not purport to be
experts in the laws of any jurisdiction other than the State of Texas and the
United States of America.
<PAGE>
Luminex Corporation
September 27, 2000
Page 2
Based solely upon the foregoing, and limited in all respects as stated
above, we are of the opinion that the Shares registered pursuant to the
Registration Statement have been duly and validly authorized by the Company, and
when sold, issued and delivered in the manner and for the consideration
described in the Plan, will be validly issued, fully paid and nonassessable.
We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement. In granting this consent, we do not thereby admit that
we come within the category of persons whose consent is required pursuant to
Section 7 of the Act or the rules or regulations of the Commission thereunder.
Respectfully submitted,
/s/ Thompson & Knight L.L.P.
