Fusarium proliferatum (NRRL 26517), was isolated by screening soil samples surrounding decaying corn and wood using corn fibre xylan as carbon source. The extracellular xylanase from this fungal strain was purified 975-fold to homogeneity from the culture supernatant by ammonium sulphate treatment. DEAE Bio-Gel A column chromatography, octyl-Sepharose column chromatography and Bio-gel A-0.5 m gel filtration. The purified xylanase (specific activity 591 U mg(-1) protein) was a monomeric glycoprotein with a molecular weight (MW) of 22 400 as determined by SDS-PAGE. The optimum pH and temperature for the action of the enzyme were at 5.0-5,5 and 55 degreesC, respectively. The purified xylanase was fully stable at pH 5.0-7.5 and temperature up to 55 degreesC. It hydrolyzed a variety of xylan substrates mainly to xylobiose and higher short-chain xylooligosaccharides. No xylose was formed. The enzyme did not require metal ions for activity and stability. Published by Elsevier Science Ltd.