EXHIBIT 99.1 CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350 AS ADOPTED PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 Pursuant to Section 1350, Chapter 63 of Title 18, United States Code, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, the undersigned, as Chief Executive Officer of Southwest Bancorporation of Texas, Inc. (the "Company"), does hereby certify that: 1) the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2003 (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 Company's Report fairly presents, in all material respects, the financial condition and results of operations of the Company. Dated: April 30, 2003 /s/ Paul B. Murphy, Jr. ---------------------------------------- Paul B. Murphy, Jr. Director, President and Chief Executive Officer