Primary biliary cirrhosis (PBC) is a progressive cholestatic liver disease frequently leading to development of cirrhosis and its complications. Ursodeoxycholic acid (UDCA) is a beneficial medical therapy for patients with PBC. Improvement in some histological features, but not in histological stage, has been reported after 2 years of UDCA therapy. Thus, longer follow-up may be necessary to determine whether UDCA has a favorable effect on histological stage of disease and progression to cirrhosis. Our aim was to determine the long-term effects of UDCA therapy on histological stage and progression to cirrhosis in patients with PBC. Sixteen unselected patients with noncirrhotic PBC who had been on long-term UDCA therapy (13-15 mg/kg/d) for 6.6 +/- 0.4 years (range, 5-9 years) were identified and their histological finding during treatment compared with that of 51 noncirrhotic patients with PBC who had received ineffective therapy (D-penicillamine [DPCA] or placebo) for 5.6 +/- 0.07 years (range, 5-8 years). Histological stage was determined using the Ludwig classification. The rate of progression to cirrhosis (stage 4) was significantly less in the UDCA group than in the control group (13% vs. 49%; P =.009). Although the overall rate of progression of histological stage was less in the UDCA group than in the control group (50% vs. 71%), this difference was not significant (P =.1). A marked improvement in liver biochemistries and Mayo risk score was noted in all patients during UDCA therapy; however, this improvement was not significantly different between patients who progressed and those who did not. In conclusion, long-term UDCA therapy appeared to delay the development of cirrhosis in PBC.