A mycoparasitic Trichoderma viride strain was investigated for the production of extracellular enzymes important in antagonism, by using natural and chromogenic substrates. Some of these enzymes, such as beta-1,3-glucanases, and low levels of proteases were produced constitutively. Under inductive conditions, the measurable activities of beta-1,3-glucanase, protease and aspecific chitinase increased, while for the proteases and beta-1,3-glucanases, the levels depended on both the nitrogen and the carbon source. Gel filtration chromatography revealed at least 4 beta-1,3-glucanases, 6 proteases, 2 beta-glucosidases and 1 beta-1,4-N-acetyl-glucosaminidase izoenzyme under inductive conditions.