An inducible mycelial β-glucosidase from Scytalidum thermophilum was characterized. The enzyme exhibited a p I of 6.5, a carbohydrate content of 15%, and an apparent molecular mass of about 40 kDa. Optima of temperature and pH were 60 °C and 6.5, respectively. The enzyme was stable up to 1 h at 50 °C and exhibited a half-life of 20 min at 55 °C. The enzyme hydrolyzed p-nitrophenyl-β- d-glucopyranoside, p-nitrophenyl-β- d-xylopyranoside, o-nitrophenyl-β- d-galactopyranoside, p-nitrophenyl-α-arabinopyranoside, cellobiose, laminaribiose and lactose. Kinetic studies indicated that the same enzyme hydrolyzed these substrates. β-Glucosidase was activated by glucose or xylose at concentration varying from 50 to 200 mM. The apparent affinity constants ( K 0.5) for glucose and xylose were 36.69 and 43.24 mM, respectively. The stimulatory effect of glucose and xylose on the S. thermophilum β-glucosidase is a novel characteristic which distinguish this enzyme from all other β-glucosidases so far described.