Budd-Chiari syndrome (BCS) occurs as a result of obstruction of hepatic venous outflow at any level from the small hepatic veins to the junction of the inferior vena cava with the right atrium. Diagnosis can be difficult because of the wide spectrum of presentation of the disease and the varying severity of liver damage. The traditional classification of BCS--as fulminant, acute or chronic--is not prognostically useful. This makes assessing the benefit of therapy difficult, especially as there is no evidence from randomized studies. This article highlights advances in the prognosis and therapy of BCS. Identification of the site of venous obstruction has a major effect on prognosis. Portal-vein thrombosis occurs in 20-30% of cases, and acute presentation of BCS reflects an acute or chronic syndrome in 60% of BCS cases. BCS can be diagnosed and treated on a single occasion in the setting of the radiology department, with hepatic venography, transjugular liver biopsy, retrograde CO2 portography and inferior vena cava pressure measurements performed simultaneously with therapies such as dilation or stenting of webs in the inferior vena cava or hepatic veins, and placement of transjugular intrahepatic portosystemic shunts. Disruption of a portal vein thrombus can also be done during the same session. Surgical shunts have been superseded by the use of transjugular intrahepatic portosystemic shunts. Liver transplantation is reserved for fulminant and progressive chronic forms of BCS. Anticoagulation therapy must be used routinely, before and after specific therapy, regardless of whether a thrombophilic disorder is diagnosed.