The effect of different sugars on the cellulase system (total cellulase, avicelase, endoglucanase, and beta -glucosidase) of Clostridium papyrosolvens CFR-703 was investigated under anaerobic fermentation conditions. Trehalose, lactose and cellobiose induced total cellulase activity of 26, 13.7 and 15.5 IU/ml, respectively. With the exception of trehalose, a concentration of >2% of these inducers inhibited production of all components of cellulase in the cultivation medium, This is the first time trehalose has been reported to be an inducer of cellulase synthesis, suggesting its industrial potential for the production of the cellulase complex especially total cellulase and avicelase required for commercial applications.