During the 10-year period from 1 January 1975 to 31 December 1984, primary sclerosing cholangitis (PSC) was diagnosed in 45 patients. Twelve of the patients have died (26.7%), 10 of them of causes related to PSC. Inflammatory bowel disease was found in all patients; ulcerative colitis was found in 37, Crohn's disease in 6, and unclassified colitis in 2 patients. Of the patients alive, 27 were submitted to a follow-up study in 1985. At the follow-up examination no general progression of the liver disease, as measured on the basis of clinical examination and levels of transaminases, alkaline phosphatases, and bilirubin, was found. Cholangiographic evaluation in 24 patients showed that the stage of ductal changes progressed from mild to moderate in 3 patients; in the other patients the stage was not altered. Morphologic examination of liver biopsy specimens in patients with a benign clinical course usually showed portal inflammation, fibrosis, and minor signs of piecemeal necrosis, whereas widespread piecemeal necrosis was found in patients who deteriorated and died. The 50% survival since diagnosis of liver disease was calculated to be 17 years in patients with PSC and 50 years in a comparable group among the general population. The estimated survival curve in PSC was displaced to the left, indicating a reduced life expectancy of about 30 years.