Trichoderma viride C-1 strain was irradiated with UV until the survival level of 0.03% was obtained. Sixteen mutants were isolated on the basis of the visible clearance zone around the colonies on the media with cellulose and glycerol. Then they were cultivated on a rotary shaker in the liquid Saunders medium supplemented with microcrystalline cellulose and comminuted sugar beet pulp. Exo-1,4-beta-glucanase, endo-1,4-beta-glucanase and beta-glucosidase were assayed in the supernatants of postcultural liquids at different time intervals of culture. The same mutants were characterized by higher biosynthesis level of exoglucanase (1.2-5.0 times) endoglucanase (1.2-2.5 times) and beta-glucosidase (1.5-1.7 times) when compared with the wild type strain.