Primary sclerosing cholangitis (PSC) is a chronic inflammatory disease associated in 10% to 36% of those with hepatobiliary malignancies, which are, in the majority of cases, not known prior to transplantation. Diagnosis of carcinomas in a PSC setting at an early stage has not yet been achieved, because there are no differences in the age of patients or clinical course, particularly with regard to the time between diagnosis of PSC and detection of carcinomas. To assess optimal timing for transplantation in patients with PSC, we applied the Mayo survival model to 48 patients receiving transplants for that disease in our center between 1972 and 1994. Of these patients, 10 had a biliary malignancy, which was incidental in 9. According to the Mayo model, low-, moderate-, and high-risk groups of patients could be formed. The actuarial patient survivals at 1 and 7 years were 100% and 100% (low risk), 68.6% and 68.6% (moderate risk), and 54.6% and 46.8% (high risk), respectively. Patients with a biliary malignancy had a 30% survival at 1 year; none survived 6 years. Local recurrence of the tumor was found in 3 patients, 2 of them with low tumor stages at the time of transplantation. Analysis of the Mayo Model risk scores demonstrated a marked increase in the incidence of biliary malignancies at a score above 4.4. All patients with tumors were found to have a score above 4. Moreover, the prevalence rate rose from 14.3% in the low-risk group to 33.3% in the moderate-risk group. There was no difference in the clinical courses at 6 to 12 months prior to transplantation; in particular, the bilirubin levels (PSC alone, 250 ± 230 mumol/L; PSC with carcinoma, 288 ± 182 mumol/L) did not differ significantly (P > .05) between both patient groups. Because the outcome after transplantation is poor even in patients with low-grade malignancies, early timing of transplantation in patients with PSC is suggested to prevent formation of biliary malignancies. Therefore, regular scoring of patients with the Mayo Model risk score is suggested, and transplantation should be taken into consideration at scores above 4.