Chaetomium cellulolyticum produced three xylanases with molecular weights of 25, 47, and 57 kDa and pIs of 8.9, 8.4, and 5.0, respectively. According to their biochemical characteristics and specificity, the 25- and 47-kDa xylanases were related to the family of G and the 57-kDa xylanase to the family of F. These xylanases had a neutral pH optimum within the range of 6-7 and the 25-kDa xylanase maintained high activity at alkaline pH up to 10. An important characteristic of the 25-kDa xylanase was its high stability at pH 9. Bleaching effects of xylanases from C. cellulolyticum on eucalyptus pulp were examined. The 25-kDa xylanase had higher than other xylanases isolated and commercial preparation Ecopulp TX 200 biobleaching activity at pH 9. All of the xylanases exhibited endo-action patterns, slight differences in the ratio of low-molecular weight sugars were detected. Changes in molecular weight distributions of xylan were observed to be the same for xylanases from C. cellulolyticum confirming the endo-mode of action of these enzymes.