A thermostable xylanase purified from a strain of Bacillus amyloliquefaciens MIR 32 was characterized with respect to its substrate specificity and mode of hydrolytic action. The enzyme was highly specific for xylans as substrate and displayed no activity toward other polysaccharides, including cellulose. The enzyme exhibited K-m and V-max of 4.5 mg/mL and 0.58 mmol/min/mg, respectively, with birchwood xylan as the substrate. Microdialysis sampling with anion exchange chromatography and integrated pulsed electrochemical detection were used for rapid on-line monitoring of products during hydrolysis of oat spelt and bagasse xylan, and xylooligosaccharides. Xylobiose and xylotriose were the main end products. Xylotetraose was the smallest oligosaccharide to be acted on by the xylanase. The product pattern confirmed that the enzyme was an endoxylanase.