The cellulase system with a maximum FP cellulase activity of 1.30 IU/ml obtained from fermentation by T. reesei of alkali treated, steamed rice straw was employed at 26 FPUg(-1) substrate for enzymatic saccharification. Production of reducing sugars (as glucose) at 268.5 mg(-1) of rice straw treated with 4% sodium hydroxide in combination with 60 min of steam pressure (1.05 kg cm(-2)) was obtained in 48 h of incubation. Analysis of variance applied to the results of the effects of various factors revealed that a substrate concentration of 4% (w/v), a pH of 5.0, a temperature of 50 degrees C, an enzyme concentration of 25 FPU g(-1) substrate and a time of 48 h, were optimum for the production of the maximum amount of reducing sugars; 268.5 mg g(-1) of pre-treated rice straw representing a maximum saccharification of 54.3% (cellulose basis).