A strain of Aspergillus versicolor produces a xylanolytic complex containing two components, the minor component being designated xylanase II. The highest production of xylanase II was observed in cultures grown for 5 days in 1% wheat bran as carbon source, at pH 6.5. Xylanase II was purified 28-fold by DEAE-Sephadex and HPLC GF-510 gel filtration. Xylanase II was a monomeric glycoprotein, exhibiting a molecular mass of 32kDa with 14.1% of carbohydrate content. Optimal pH and temperature values for the enzyme activity were about 6.0-7.0 and 55 o C, respectively. Xylanase II thermoinactivation at 50 o C showed a biphasic curve. The ions Hg 2 + , Cu 2 + and the detergent SDS were strong inhibitors, while Mn 2 + ions and dithiothreitol were stimulators of the enzyme activity. The enzyme was specific for xylans, showing higher specific activity on birchwood xylan. The Michaelis-Menten constant (K m ) for birchwood xylan was estimated to be 2.3mgml - 1 while maximal velocity (V m a x ) was 233.1μmolmg - 1 min - 1 of protein. The hydrolysis of oat spelt xylan released only xylooligosaccharides.