Ursodeoxycholic acid (UDCA) has been claimed to reduce the risk of biliary pain, regardless of gallstone dissolution. In a large study by Tomida et al., risks of biliary pain or gallstone complications (acute cholecystitis) were reduced in both symptomatic and asymptomatic gallstone carriers, although gallstones were generally not dissolved. Also, biliary pancreatitis might be prevented by long-term UDCA treatment. Increased fasting and residual postprandial gallbladder volumes during UDCA treatment, less cholesterol crystals or decreased mucin contents in bile could be the underlying mechanisms for these beneficial effects. However, prospective studies on effects of UDCA on symptoms or complications in highly symptomatic patients are lacking.