Summary Extracellular enzymes produced by Trichoderma harzianum and T. polysporum in single and mixed cultures and Scytalidium lignicola were investigated. T. harzianum produced at least 12 polypeptides in malt extract broth of between 18 and 117 kd and T. polysporum produced 8 polypeptides of 19 to 127 kd. Fewer polypeptides were produced on Czapek-Dox medium and additional components were synthesized in mixed cultures. A range of extracellular hydrolytic enzyme activities were detected including acid and alkaline phosphatases, esterase, lipase, leucine arylamidase, Phosphoamidase, α- and s-galactosidases, α-and s-glucosidases, N-acetyl-s-glucosaminidase and protease. Pellets containing propagules of T. harzianum, T. polysporum and S. lignicola (Binab T and FYT pellets) also contained exoenzymes. The results are discussed in relation to biological control.