Chaetomium erraticum was capable of producing all the three components of a cellulase enzyme system including exoglucanase, endoglucanases, and -glucosidase extracellularly. However, the cultivation conditions and the medium composition markedly affected the ability of microorganism to synthesize various enzymes. Exoglucanase was highest under static conditions, while endoglucanase and -glucosidase were maximized under shake conditions. Among the various defined substrates, CMC proved to be the best inducer for exoglucanase under static conditions and -glucosidase under shake conditions. MCC induced maximum endoglucanase under shake conditions. The biosynthesis of all three components of cellulases was repressed with different concentrations of glucose, puromycin, actinomycin, and actidione, while the supplementation of exogenous cyclic-AMP was fully capable of releasing the catabolite repression for production of all three components.