The hepatorenal syndrome is a severe and common complication of patients with advanced cirrhosis and ascites. It is characterised not only by renal failure but also by marked alterations in systemic haemodynamics. Renal failure is due to a marked hypoperfusion of the kidney secondary to renal vasoconstriction. Although the pathogenesis of hepatorenal syndrome is not completely understood, it is thought to be the extreme manifestation of the underfilling of the arterial circulation secondary to an arterial vasodilation, located mainly in the splanchnic circulation. Recently, a revised definition and diagnostic criteria of hepatorenal syndrome have been proposed. The prognosis of patients with hepatorenal syndrome is very poor. Liver transplantation is the only effective treatment but it is not applicable in most cases due to short survival. New therapies developed during the last years, such as the use of systemic vasoconstrictors or transjugular intra-hepatic portosystemic shunts appear to be promising, but prospective investigations are needed to delineate their real usefulness.