A basic xylanase was purified from the culture supernatant of thermoalkaliphilic Bacillus sp. strain TAR-1. Its molecular mass and isoelectric point were 23 kDa and > pH 9.3, respectively. The enzyme showed a broad pH profile and was optimally active at 70 degrees C. Analyses of xylan-degradation products and N-terminal amino acid sequence revealed that the enzyme would be a family 11/G endoxylanase.