Exhibit 32.1



                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002


In connection with the Quarterly  Report of NL Industries,  Inc. (the "Company")
on Form 10-Q for the period ended June 30, 2003 as filed with the Securities and
Exchange  Commission on the date hereof (the  "Report"),  we, Harold C. Simmons,
Chief Executive Officer of the Company, and Gregory M. Swalwell, Vice President,
Finance of the Company,  certify, pursuant to 18 U.S.C. Section 1350, as adopted
pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

     (1) The Report fully  complies  with the  requirements  of Section 13(a) or
15(d) of the Securities Exchange Act of 1934; and

     (2)  The  information  contained  in the  Report  fairly  presents,  in all
material  respects,  the  financial  condition  and result of  operations of the
Company.




/s/  Harold C. Simmons                        /s/  Gregory M. Swalwell
     ------------------------                      -------------------------
     Harold C.Simmons                              Gregory M. Swalwell
     Chief Executive Officer                       Vice President, Finance
     October 31, 2003                              October 31, 2003



Note: The certification  the registrant  furnishes in this exhibit is not deemed
"filed" for purposes of Section 18 of the  Securities  Exchange Act of 1934,  as
amended,  or otherwise subject to the liabilities of that Section.  Registration
Statements or other documents filed with the Securities and Exchange  Commission
shall not incorporate this exhibit by reference,  except as otherwise  expressly
stated in such filing.