The effect of glucose, cellobiose and xylose on the regulation of cellulolytic activity in Cellulomonas sp. IIbc was investigated. The addition of 1% glucose, cellobiose or xylose to actively growing bagasse pith cultures repressed the cellulose system. No enzyme inactivation by sugar concentrations up to 1.5% was detected. Both cellobiose and xylose, at concentrations ranging form 0.005 to 0.02%, served as inducers of the cellulolytic complex in resting cell experiments, while a basal level of constitutive synthesis occurred without any cellulosic substrate or derivative in the culture medium. (C) 1996.