The partitioning of xylanase, produced by solid-state cultivation of Polyporus squamosus, in aqueous two-phase system polyethylene glycol/ammonium sulphate was studied. In system 10% (w/w) polyethylene glycol 1500/20% (w/w) ammonium sulphate/70% (w/w) crude enzyme at pH 5.1 favourable partition coefficient and the top phase yield were obtained, 85.6% and 97.37%, respectively, followed by purification factor 4.8. This result suggests the possible integration of cultivation and primary downstream processing step by partitioning of xylanase in aqueous two-phase system. (C) 2005 Elsevier Ltd. All rights reserved.