1. Skin Type I collagen was isolated from 15 species of teleosts. 2. Chromatographic and electrophoretic analyses revealed that most of the teleost skin collagens possessed a unique subunit, alpha 3, which had not been detected in other vertebrate Type I collagens. 3. The skin collagen seems to exist as an alpha 1 alpha 2 alpha 3 heterotrimer in many teleosts and as an (alpha 1)2 alpha 2 heterotrimer in some teleosts.