the cellulolytic complex of trichoderma longibrachiatum was separated into nine fractions using fplc. the avicelase, cellobiase, carboxymethylcellulase, and endoglucanase activities of these fractions were characterized. the endoglucanase activity was measured by a method that allows the determination of the variation of the degree of polymerization of the insoluble celluloses. this method, which is based on measuring the reducing power of the insoluble fibers, is proposed as a tool for the identification and characterization of the endoglucanases. using this technique and h//3po//4-swollen cotton as substrate, the kinetic parameters of two proteins that showed high specific endoglucanase activity (pi $equals$ 5.25; m//r $equals$ 55 kda and pi $equals$ 4.70; m//r $equals$ 70 kda) were determined. the measurement of the degree of polymerization variation during digestion of sigmacell gives evidence that the endoglucanase activity occurs at the beginning of the reaction. (edited author abstract) 26 refs