In patients with primary biliary cirrhosis (PBC), ursodeoxycholic acid (ursodiol) improves laboratory test markers of cholestasis and hepatic inflammation as well as some hepatic histological features; it also delays histological progression in the early stages of PBC. Ursodiol is well tolerated and safe. Less well substantiated are that ursodiol either improves the quality of life or prevents liver transplantation or that it prolongs survival without transplantation. There are favorable trends for ursodiol in preventing transplantation and prolonging survival, but in the absence of randomized, placebo-controlled trials of sufficient duration, there remain impressions rather than statistically proved, strong conclusions.