The concentration of immunoglobulins and immune complexes was determined in the serum and bile of four patients with primary sclerosing cholangitis, only one of whom had chronic ulcerative colitis, and in four postcholecystectomy control patients. The result of the immunoglobulin studies demonstrated increased serum levels of IgM in primary sclerosing cholangitis as compared to control patients. The IgG, IgA, and IgM in bile were all significantly elevated as compared to controls (p = 0.02). Immune complexes in bile and serum were also determined in both groups by the C1q and conglutinin binding assays. Immune complexes in bile were elevated in three of four of the patients with primary sclerosing cholangitis. These findings further characterize primary sclerosing cholangitis in terms of biliary immunoglobulins and immune complexes but do not resolve whether these changes are an epiphenomenon or reflect a primary role of immunoglobulins and immune complexes in the pathogenesis of this disorder.