A central composite orthogonal design model was used to optimize pretreatment and culture conditions for the production of cellulase-systems by T. reesei QMY-1 and MCG 80 using wheat straw as carbon source. The model was capable of predicting conditions for maximum filter paper activity (FPA) and beta-glucosidase activity (beta GA). Statistical analysis showed close agreement between the experimental FPA and beta GA activities and predicted values. Maximum FPA of 9.88 IU/ml and 8.38 IU/ml were obtained for T. reesei MCG 80 and T. reesei QMY-1, respectively, using 4% NaOH pretreatment and initial culture pH 6, under solid-state fermentation conditions. The cellulase-systems produced were capable of hydrolyzing over 80% delignified wheat straw. Combination of NaOH pretreatment with steam explosion did not enhance the activity of the cellulase-systems of the two mutants.