Exhibit 99.1

    CERTIFICATION PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the filing of the Quarterly Report on Form 10-Q for the
quarter ended March 31, 2003 (the "Report") by Kirby Corporation (the
"Company"), each of the undersigned hereby certifies that:

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

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

                                           /s/ J. H. PYNE
                                           -------------------------------------
                                           J. H. Pyne
                                           President and Chief Executive Officer

                                           /s/ NORMAN W. NOLEN
                                           -------------------------------------
                                           Norman W. Nolen
                                           Executive Vice President, Treasurer
                                              and Chief Financial Officer

Dated: May 9, 2003

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