Hepatorenal syndrome is a functional renal failure that occurs in cirrhotic patients with advanced liver disease and ascites. The diagnostic criteria and clinical types of this syndrome have recently been revised. Hepatorenal syndrome is caused by marked hypoperfusion of the kidney as the result of renal vasoconstriction, which is thought to be the extreme manifestation of an underfilling of the arterial circulation. This circulatory dysfunction is the consequence of arterial vasodilation in the splanchnic circulation. Liver transplantation is the best treatment for HRS, but its applicability is low because of the short survival of these patients. New therapies, such as the use of systemic vasoconstrictors or TIPS, seem promising, but prospective investigations are needed to delineate their role in the management of cirrhotic patients with HRS.