Collagens from marine invertebrates were obtained by pepsin treatment of the collagenous tissues such as the mantle of pearl oyster, the body walls of squid and octopus, and the subcuticular tissues of spiny lobster and blue crab, because of the low solubility of these collagens. The invertebrate collagens have the same fundamental molecular properties as vertebrate collagens. The thermal stability of the collagens corresponds to that of collagens from warm-water fishes and the denatured collagens contain both α-and β-components. The invertebrate collagens are rich in hydroxylysine, acidic amino acids, amide nitrogen, and carbohydrate as compared with vertebrate collagens. The ratios of hydroxylysine to lysine are always higher than those for vertebrates. 3-Hydroxyproline as well as 4-hydroxyproline was found in all the preparations.