EXHIBIT 10.18

                             THIRD AMENDMENT TO THE
                          MANAGEMENT SERVICES AGREEMENT

         THIS THIRD AMENDMENT TO THE MANAGEMENT SERVICES AGREEMENT dated August
12, 2002 is entered into and effective this 11th day of December, 2003 by and
between Luminex Corporation, a Delaware corporation (the "Company") and Thomas
W. Erickson ("Erickson").

         WHEREAS, the Company and Erickson desire to continue the management
services delivered pursuant to the Management Services Agreement dated August
12, 2002 (the "Agreement").

         NOW, THEREFORE, the parties execute this Third Amendment to the
Agreement:

         1.       The substantive terms, covenants and agreements shall continue
                  for a Term from January 1, 2004 through March 31, 2004.

         2.       Cash compensation shall continue at the same rate for
                  Erickson's services hereunder.

         3.       An additional option grant of 37,500 shares of the Company's
                  common stock shall be granted on the date of this agreement
                  pursuant to the terms and conditions of the Option Agreement
                  to be executed simultaneously herewith, in the form attached
                  hereto as Exhibit A (the "Option Agreement"). Notwithstanding
                  the foregoing, the exercise price per share shall be equal to
                  the closing sale price on the date of grant and vesting shall
                  occur in one third increments on the last day of each month of
                  January through March, 2004, all as set forth in the Option
                  Agreement.

         All other terms of the Agreement shall continue and all capitalized
terms not otherwise defined will have such meaning as set forth in the
Agreement.

         IN WITNESS WHEREOF, this Third Amendment is executed by the parties as
of the effective date set forth above.

                                              LUMINEX CORPORATION

                                              By: /s/ Harriss T. Currie
                                                  ------------------------------

                                              Title: Chief Financial Officer

                                                  /s/ Thomas W. Erickson
                                                  ------------------------------
                                              Thomas W. Erickson

                              Luminex Confidential