Recurrence of primary sclerosing cholangitis (PSC) following liver transplantation has been suggested; however, it has not been fully defined because of numerous complicating factors and the lack of diagnostic criteria. In the present study, we investigated the recurrence of PSC by developing strict criteria and applying them to a large cohort of PSC patients who underwent liver transplantation. Between March 1985 and June 1996, 150 PSC patients underwent liver transplantation at the Mayo Clinic; mean follow up was 55 months. The incidence of nonanastomotic biliary strictures and hepatic histologic findings suggestive of PSC were compared between patients transplanted for PSC and a non-PSC transplant control group. Our definition of recurrent PSC was based on characteristic cholangiographic and histologic findings that occur in nontransplant PSC patients. By using strict criteria, 30 patients with other known causes of posttransplant nonanastomotic biliary strictures were excluded leaving 120 patients for analysis of recurrence of PSC. We found evidence of PSC recurrence after liver transplantation in 24 patients (20%). Of these, 22 out of 24 patients showed characteristic features of PSC on cholangiography and 11 out of 24 had compatible hepatic histologic abnormalities with a mean time to diagnosis of 360 and 1,350 days, respectively. Both cholangiographic and hepatic histologic findings suggestive of PSC recurrence were seen in nine patients. The higher incidence and later onset of nonanastomotic biliary strictures in patients with PSC compared with a non-PSC control group is supportive of the fact that PSC does recur following liver transplantation. We were unable to identify specific clinical risk factors for recurrent PSC, and the overall patient and graft survival in patients with recurrent PSC was similar to those without evidence of recurrence. Our observations provide convincing evidence that PSC frequently recurs in the hepatic allograft using strict inclusion and exclusion criteria.