Collagen has been prepared from the skin of an air-breathing Indian fish(Ophiocephalus striatus) by extraction with cold 0.5M acetic acid and purification by alternate precipitation with NaCl and dialysis against 0.02M Na2HPO4. The purified collagen was characterised with respect to physico-chemical properties, amino acid composition and chromatography of the denatured collagen. The fish collagen has a higher shrinkage temperature and denaturation temperature compared to that of the allied teleosts living in exclusively aquatic medium. These differences could possibly be reflections of the response to the rigours of the environment. As found for other vertebrate collagens, the fish collagen contains two kinds of single chains the α1 and α2 chains as revealed by sodium dodecyl sulphate-polyacrylamidegel electrophoresis and carboxymethylcellulose chromatography.