EXHIBIT 99.1

      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 Quarterly
Report of National  Instruments  Corporation on Form 10-Q for the fiscal quarter
ended March 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-Q 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, Alex 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 Quarterly Report of
National Instruments Corporation on Form 10-Q for the fiscal quarter ended March
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-Q
fairly presents in all material respects the financial  condition and results of
operations of National Instruments Corporation.

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