An alkalophilic Bacillus sp Sam-3, producing high levels of cellulase-free xylanase active and stable at alkaline pH was isolated from a soda lake. When grown in shake flasks for 48 h on agricultural residues such as wheat bran supplemented with yeast extract, the culture produced 131 IU ml(-1) enzyme activity. The optimum pH and temperature of the enzyme were 8 and 60 degrees C, respectively. The enzyme retained approximately 75% of its activity at pH 8 and 60 degrees C when incubated for 2 h. Enzymatic treatment of bagasse pulp carried out using 1.2 IU of enzyme per gram of pulp at 60 degrees C and pH 8 for 2 h resulted in a 4 unit decrease in the kappa number. Similar treatment of the pulp at pH 7 and 9 indicated that the Sam-3 xylanase was effective in reducing the kappa number of the pulp over a wide pH range.