Treatment of patients with primary biliary cirrhosis (PBC) using ursodeoxycholic acid (UDCA) leads to a reduction in serum bilirubin. The first objective of this study was to assess the performance of certain prognostic indicators for PBC after the introduction of treatment with UDCA. Serum bilirubin is an important prognostic indicator for PBC and an important component of the Mayo model for grading patients into risk categories. In an analysis of patients enrolled in the Canadian multicenter trial, the Mayo score was calculated before and after treatment with UDCA. After treatment, the Mayo score continued to divide patients with PBC into groups with varying risk. In addition, the serum bilirubin alone was shown to do the same even after the introduction of treatment with UDCA. A second objective was to establish whether UDCA had an effect on long-term (2- to 6-year) survival in patients with PBC.