Hepatorenal syndrome (HRS) is a functional renal failure that frequently develops in patients with advanced cirrhosis and severe impairment in systemic circulatory function. Traditionally it has been considered to be the consequence of a progression of the splanchnic arterial vasodilation occurring in these patients. However, recent data indicate that a reduction in cardiac output also plays a significant role. There are two different types of HRS. Type-2 HRS consists of a moderate and steady or slowly progressive renal failure. It represents the extreme expression of the circulatory dysfunction that spontaneously develops in patients with cirrhosis. The main clinical problem in these patients is refractory ascites. Type-1 HRS is a rapidly progressive acute renal failure that frequently develops in closed temporal relationship with a precipitating event, commonly spontaneous bacterial peritonitis. In addition to renal failure, patients with type-1 HRS present deterioration in the function of other organs, including the heart, brain, liver, and adrenal glands. Type-1 HRS is the complication of cirrhosis associated with the worst prognosis. However, effective treatments of HRS (vasoconstrictors associated with intravenous albumin, transjugular intrahepatic portacaval shunt, albumin dialysis) that can improve survival have recently been introduced.