In this study we investigated the use of a crude enzyme extract from Trichoderma viride to hydrolyze wheat straw for butanol production by Clostridium acetobutylicum ATCC824. Prior to fermentation, the wheat straw was hydrolyzed by the crude enzyme at the optimized conditions of 50.7 degrees C, pH 5.1, 41.1 IU/g cellulase dosage, and 38.1 g/L substrate concentration, in which the sugar yield was 17.32 g/L, resulting in a 82.2% saccharification efficiency of commercial cellulase. The final butanol concentration, yield, and maximum productivity, 7.05 g/L, 0.155 g/g of glucose, and 0.141 g/L.h, were observed in separated hydrolysis and fermentation after 54 h of fermentation using 2-fold concentrated hydrolysate. Simultaneous saccharification and fermentation was also investigated, and appreciable butanol concentration, yield, and productivity of 5.05 g/L, 0.127 g/g of glucose, and 0.080 g/L.h were attained. The results described here are comparable to those obtained by using commercial cellulase and clearly indicate the potential application of crude cellulase for enhanced butanol production from lignocellulose.