There is no effective medical treatment for primary sclerosing cholangitis (PSC), a chronic cholestatic liver disease that usually progresses to cirrhosis and liver failure. The aim of this study was to determine the safety and efficacy of etanercept, an inhibitor of tumor necrosis factor, in the treatment of PSC. Ten patients with clinically active PSC were studied. All had elevated serum alkaline phosphatase levels, cholangiograms that were diagnostic of PSC, and liver histology consistent with PSC. Five patients had elevated serum bilirubin levels, five had pruritus, eight had failed to respond to ursodiol and/or methotrexate, and six had rapidly recurring dominant bile duct strictures. Patients were to receive etanercept, 25 mg subcutaneously twice weekly, for 6 months if there were no side effects and for 1 year if there was evidence of efficacy after 6 months. Biochemical tests of liver function did not improve in any patient. Mean serum bilirubin levels increased significantly, from 2.0 to 3.6 mg/dl (P = 0.026). Two of the five patients with pruritus had resolution of pruritus during treatment with etanercept, recurrence when etanercept was stopped, and resolution when it was restarted, although there was little change in liver enzymes or bilirubin levels. There was no decrease in the rate of stricture formation and there were no side effects. Etanercept, at the dosage used, was well tolerated but not effective in the treatment of PSC. It may be helpful in treating pruritus due to cholestasis.