EXHIBIT 99.1 CERTIFICATION PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 (SUBSECTIONS (a) AND (b) OF SECTION 1350, CHAPTER 63 OF TITLE 18, UNITED STATES CODE) Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (Subsections (a) and (b) of Section 1350, Chapter 63 of Title 18, United States Code) (the "Act"), I, R. Steve Letbetter, President and Chief Executive Officer (and principal financial officer) of Reliant Energy Resources Corp. (the "Company"), hereby certify, to the best of my knowledge: (1) The Company's Quarterly Report on Form 10-Q for the quarter ended June 30, 2002 (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 results of operations of the Company. Dated: August 14, 2002 /s/ R. Steve Letbetter -------------------------------- R. Steve Letbetter President and Chief Executive Officer (and principal financial officer) The foregoing certification is being furnished solely pursuant to Section 906 of the Act and is not being filed as part of the Report or as a separate disclosure document.