BACKGROUND & AIMS: Long-term ursodeoxycholic acid (UDCA) therapy slows the progression of primary biliary cirrhosis. This study examined the effect of UDCA therapy on survival free of liver transplantation in a large group of patients. METHODS: Data from three clinical trials were combined in which patients with primary biliary cirrhosis were randomly assigned to receive UDCA (n = 273) or placebo (n = 275). After 2 years, patients from French and Canadian studies received UDCA for up to 2 years. Patients from the American study remained on their assigned treatment for up to 4 years. RESULTS: Survival free of liver transplantation was significantly improved in the patients treated with UDCA compared with the patients originally assigned to placebo (P < 0.001; relative risk, 1.9; 95% confidence interval, 1.3-2.8). Subgroup analyses showed that survival free of liver transplantation was significantly improved in medium- and high-risk groups (serum bilirubin level, 1.4 to 3.5 or > 3.5 mg/dL; P < 0.0001 and P < 0.03, respectively) and histological stage IV subgroup (P < 0.01). CONCLUSIONS: Long-term UDCA therapy improves survival free of liver transplantation in patients with moderate or severe disease. An effect in patients with mild disease is probably not found because they do not progress to end-stage disease in 4 years. (Gastroenterology 1997 Sep;113(3):884-90)