We have seen 13 patients with sclerosing cholangitis diagnosed mainly by ERCP. An elevated alkaline phosphatase is frequently the first manifestation. ERCP is adequate for diagnosis, and an operation is usually not necessary. Radiologic findings include diffuse and irregular areas of stenosis, dilation, beading, and extensive involvement of both the extrahepatic and intrahepatic biliary radicles. There was an association with long-standing ulcerative colitis, but no relationship with activity of this disease or its complications. Liver biopsy in 10 of 11 patients demonstrated very little progression of disease, and evidence of secondary biliary cirrhosis was found in only one case. Corticosteroid therapy was used in 10 patients without clinical evidence that this altered their course. Prognosis appears to be reasonably good and unrelated to the course of ulcerative colitis.