Human hyaline cartilage contains three collagen chains in addition to the alpha 1(II) chain of Type II collagen. Two of these chains, tentatively designated the 1 alpha and 2 alpha chains, have been extensively characterized. Although similar in molecular weight to other collagen chains, by the combined criteria of solubility, electrophoretic mobilities, carboxymethylcellulose elution profiles, total amino acid compositions, carbohydrate contents, cyanogen bromide peptide profiles, limited V8 protease digestion profiles, and examination of selected cyanogen bromide peptides, the 1 alpha and 2 alpha chains are structurally unique collagen alpha chains. Because of similarities of the 1 alpha and 2 alpha chains to the alpha 1(V) and alpha 2(V) chains, respectively., of Type V collagen, specific comparisons between these collagen chains and their constituent peptides were made and yielded the conclusion that these chains are nonidentical, but share substantial similarities.