Cartilage is produced as a by-product from slaughter house and fishery industries in Thailand. The enzymatic extraction of chondroitin sulfate followed the method of Nakano et al. [T. Nakano, H.H. Sunwoo, X. Li, M.A. Price, S.S. Jeong, Study of sulfated glycosaminoglycans from porcine skeletal muscle epimysium including analysis of iduronosyl and glucoronosyl residues in galactosaminoglycan fractions, J. Agric. Food Chem. 44 (1996) 1424-1434] and the sulfate glycosaminoglycans (GAGs) assay [W.R. Farndale, D.J. Buttle, A.J. Barrett, Improved quantitation and discrimination of sulphated glycosaminoglycans by use of dimethylmethylene blue, Biochim. Biophys. Acta 883 (1986) 173-177] was employed to determine the content of chondroitin sulfate in cartilage of shark fin, ray, crocodile and chicken keel. Identification of types of chondroitin sulfate through FTIR spectroscopy KBr pellet technique was carried out. The results indicated that chicken keel, crocodile hyoid and sternum cartilage are the most promising potential sources of chondroitin sulfate. The value ranges from 11.55 to 14.84g/100g of dried cartilage, calculated as chondroitin-4-sulfate. Identification of dried chondroitin sulfate extracts from investigated cartilages show the existence of both chondroitin-4-sulfate and chondroitin-6-sulfate. (c) 2006 Elsevier B.V. All rights reserved.