Exhibit 99.906 CERTIFICATION 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 I, William G. Papesh, President and Chief Executive Officer of the WM Trust I (the "Funds"), certify that to my knowledge: 1. The Form N-CSR of the Funds for the period ended April 30, 2004 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 Form N-CSR of the Funds for the period ended April 30, 2004 fairly presents, in all material respects, the financial condition and results of operations of the Funds. Date: July 2, 2004 By: /s/ William G. Papesh --------------------- William G. Papesh President and Chief Executive Officer CERTIFICATION 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 I, Jeffery L. Lunzer, Treasurer and Chief Financial Officer of WM Trust I (the "Funds"), certify that to my knowledge: 1. The Form N-CSR of the Funds for the period ended April 30, 2004 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 Form N-CSR of the Funds for the period ended April 30, 2004 fairly presents, in all material respects, the financial condition and results of operations of the Funds. Date: July 2, 2004 By: /s/ Jeffery L. Lunzer ---------------------- Jeffery L. Lunzer Treasurer and Chief Financial Officer