Ursodeoxycholic acid (UDCA), the 7β-epimer of chenodeoxycholic acid, has multiple hepatoprotective activities. UDCA modifies the bile acid pool, decreasing levels of endogenous, hydrophobic bile acids while increasing the proportion of nontoxic hydrophilic bile acids. UDCA has a choleretic effect, increasing hepatocellular bile acid excretion, as well as cytoprotective, antiapoptotic, and immunomodulatory properties. UDCA has been shown to delay development of gastroesophageal varices and progression to cirrhosis as well as to improve long-term survival in patients with primary biliary cirrhosis. Significant improvement of abnormal liver tests may be achieved during UDCA therapy in patients with primary sclerosing cholangitis, intrahepatic cholestasis of pregnancy, cystic fibrosis-associated liver disease, nonalcoholic fatty liver disease, graft-versus-host disease of the liver, total parenteral nutrition-induced cholestasis, and in some pediatric cholestatic liver diseases. However, unlike the effecs of UDCA in primary biliary cirrhosis, the long-term effects of UDCA in disease progression and survival in these other conditions remain to be established.