Type AB2 collagen was isolated from normal lung parenchyma by pepsin extraction followed by differential salt extraction. This collagen comigrates with AB2 collagen isolated from placental membranes when run on 5% polyacrylamide gel electrophoresis; it has an alpha A and alpha B polypeptide chain ratio of 1 : 2 and a cyanogen bromide peptide profile similar to known AB2 collagen on 7.5% polyacrylamide gel electrophoresis. This AB2 collagen isolated from lung tissue specifically inhibits passive hemagglutination of affinity-purified rabbit antibodies to AB2 collagen isolated from amnionic and chorionic membranes. By indirect immunofluorescence microscopy, AB2 collagen was found to be widely distributed throughout the lung and was found preferentially associated with cell surfaces (basement lamina) and basement membranes.