The enzymic conversion of cellulose is catalyzed by a multiple enzyme system. The Trichoderma enzyme system has insufficient ..beta..-glucosidase (EC 184.108.40.206) activity for the practical saccharification of cellulose. Aspergillus niger and A. phoenicis were superior producers of ..beta.. glucosidase and a method for production of this enzyme in liquid culture is presented. When Trichoderma cellulase preparations are supplemented with ..beta.. glucosidase from Aspergullus during practical saccharifications glucose is the predominant product and the rate of saccharification is significantly increased. The stimulatory effect of ..beta.. glucosidase appears to be due to the removal of inhibitory levels of cellobiose.