Sera from patients with autoimmune chronic active hepatitis were found to contain IgG-class antibody to the acidic glycosphingolipid fraction from rabbit hepatocyte plasma membrane by solid-phase enzyme-linked immunosorbent assay. Using serum positive for the antibody as a probe, we isolated the target antigen by Iatrobeads column chromatography. Analysis by thin-layer chromatography and negative ion fast atom-bombardment mass spectrometry revealed that the antigen was sulfatide. The presence of antisulfatide antibody was also confirmed by immunoblotting. The reactivity of the serum with sulfatide was diminished by preincubation of the serum with galactosylceramide-6-sulfate and sulfatide, indicating that the antibody reacted with sulfated galactosylceramide regardless of the position of the sulfate residue. The antibody was found in 92.3%, 42.9%, 15.8%, 14.2%, 0% and 0%, respectively, of patients with autoimmune chronic active hepatitis, primary biliary cirrhosis, cirrhosis, systemic lupus erythematosus, chronic active hepatitis and chronic persistent hepatitis. Thus antisulfatide antibody was characteristic of autoimmune-type chronic liver diseases. Antisulfatide antibody was absorbed by rabbit hepatocyte plasma membrane. Preincubation of sera with sulfatide immobilized on Sepharose decreased their reactivities with not only sulfatide but also rabbit plasma membrane and rat hepatocytes. Therefore sulfatide may be a target antigen of the antibody to hepatocyte surface membrane.