Microcrystalline cellulose (MCC) was hydrolyzed with Trichoderma viride cellulase, linear correlation was found between free filter paper activity (FPA) and free carboxymethyl cellulase activity (CA), and between bound CA and bound protein concentration at 0-72 h reaction time. Linear correlation between bound FPA and bound protein concentration was found at short reaction time (I h), but not found at long reaction time. CA, the activity of endoglucanase, may be used to describe the adsorption of whole cellulase, at least, for MCC-T viride cellulase system. and the error for CA assay was less than which for FPA assay and protein concentration assay in hydrolysis condition. (C) 2004 Elsevier Inc. All rights reserved.