The beneficial effects of ursodeoxycholic acid (UDCA) in patients with primary biliary cirrhosis led to therapeutic trials with this bile acid for the treatment of PSC. In two prospective placebo-controlled trials, UDCA led to a significant improvement of AP, GGT, ALT, AST, and, in one study, also of serum bilirubin. In both studies liver histology improved significantly, mainly due to a decrease of cellular infiltrates in portal triads. Pruritus and fatigue improved in approximately one-third of the patients, but, compared to placebo, this effect was not significant. In a follow-up study after on average 3.1 years of UDCA treatment, 7/43 of the patients with stages I-IV disease developed a stenosis of the common bile duct which was effectively treated by endoscopic dilatations. Of 57 patients with PSC included since 1987 in the study, 14 dropped out and of these in 10 information on the outcome is available. In patients treated by UDCA and, whenever necessary, by endoscopic dilatations, the frequency of transplantations was significantly reduced in comparison to patients who dropped out of the study. Bile duct carcinoma developed in 5% of our patients. The data indicate that treatment of patients with PSC with UDCA and by endoscopic dilatations of common duct stenoses is promising. In patients with endstage disease, the only effective therapy is liver transplantation. Therefore, the early diagnosis of the disease seems very important.