The xylanolytic system of an alkali-tolerant Bacillus sp. consists of several xylanases ranging from 22 to 120 kDa and pI values from 7.0 to 9.0. Crude xylanase retained 72% of initial activity after 5 h at pH 9.0 and 45 degrees C. Xylanase production was induced by xylose and xylan and was maximum at 42 degrees C and pH 7.8. Crude xylanase released xylotriose and xylotetraose as main products of xylan hydrolysis. Xylose was not detected.