Aspergillus tamarii produced extracellular xylanase and intracellular beta-xylosidase inductively in washed glucose-grown mycelia incubated with xylan and methyl beta-D-xyloside, a synthetic glycoside. Methyl beta-D-xyloside was a more effective inducer than xylan at the same concentration for both enzymes. Glucose and cycloheximide were found to inhibit xylanase production by methyl beta-D-xyloside. Methyl beta-D-xyloside was hydrolyzed to xylose by mycelial extract in vitro.