As functional materials, chitin and chitosan offer a unique set of characteristics: biocompatibility, biodegradability to harmless products, nontoxicity, physiological inertness, antibacterial properties, heavy metal ions chelation, gel forming properties and hydrophilicity, and remarkable affinity to proteins. Owing to these characteristics, chitin- and chitosan-based materials, as yet underutilized, are predicted to be widely exploited in the near future especially in environmentally benign applications in systems working in biological environments, among others as enzyme immobilization supports. This paper is a review of the literature on enzymes immobilized on chitin- and chitosan-based materials, covering the last decade. One hundred fifty-eight papers on 63 immobilized enzymes for multiplicity of applications ranging from wine, sugar and fish industry, through organic compounds removal from wastewaters to sophisticated biosensors for both in situ measurements of environmental pollutants and metabolite control in artificial organs, are reviewed. (C) 2004 Elsevier Inc. All rights reserved.