EXHIBIT 32.1

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

I, James  Truchard,  certify,  pursuant to 18 U.S.C.  Section  1350,  as adopted
pursuant  to  Section  906 of the  Sarbanes-Oxley  Act of 2002,  that the Annual
Report of  National  Instruments  Corporation  on Form 10-K for the fiscal  year
ended December 31, 2003 fully complies with the requirements of Section 13(a) or
15(d) of the Securities  Exchange Act of 1934 and that information  contained in
such Form 10-K fairly presents in all material respects the financial  condition
and results of operations of National Instruments Corporation.

                                       By:      /s/ James Truchard
                                       Name:    James Truchard
                                       Title:   Chief Executive Officer

I, Alexander  Davern,  certify,  pursuant to 18 U.S.C.  Section 1350, as adopted
pursuant  to  Section  906 of the  Sarbanes-Oxley  Act of 2002,  that the Annual
Report of  National  Instruments  Corporation  on Form 10-K for the fiscal  year
ended December 31, 2003 fully complies with the requirements of Section 13(a) or
15(d) of the Securities  Exchange Act of 1934 and that information  contained in
such Form 10-K fairly presents in all material respects the financial  condition
and results of operations of National Instruments Corporation.

                                       By:      /s/ Alexander Davern
                                       Name:    Alexander Davern
                                       Title:   Chief Financial Officer