A xylanase produced by the brown-rot fungus, Gloeophyllum trabeum, was purified to electrophoretic homogeneity by ion-exchange chromatography and gel filtration. The enzyme had an isoelectric point of 5.0 and molecular mass of 39–42 kDa, respectively. The xylanase appeared to prefer the most substituted glucurono-xylan (DMSO-xylan) as substrate and exhibited a pH optimum of 4.0 and a temperature optimum of 80°C after 30 min incubation. Approximately 22% of the activity remained after 2 h incubation at 70°C and the half-life of xylanase at 60°C was 24 h. The xylanase also showed β-glucanase activity with barley β-glucan as substrate as side activity. The xylanase of G. trabeum was very tolerant to inhibitors. Among the various inhibitors studied, only 10 mM AlCl3 was found to inhibit the xylanase activity.