This paper studies the H2O2 decomposition using supported catalase. The supports are gamma-Al2O3, FeCl2-treated gamma-Al2O3, glutaraldehydetreated chitosan and glutaraldehyde-treated-cellulose. Catalase/gamma-Al2O3 is inactive, but the treatment with FeCl2 renders the oxide active. The extended Huckel type analysis (EHMO) indicates that the alumina-catalase interaction is strong, suggesting that a denaturation of the enzyme is accomplished when supporting on this oxide. Amongst all the samples, catalase/glutaraldehyde-cellulose is the most active, especially after 6 months of storage. After aging. catalase/glutaraldehyde-chitosan becomes inactive, probably due to the fact that NH2 groups on chitosan react with the enzyme active sites. (C) 2003 Elsevier B.V. All rights reserved.