Hepatorenal syndrome is a frequent complication in patients with cirrhosis, ascites and advanced liver failure. Its annual incidence in patients with ascites has been estimated at 8%. Hepatorenal syndrome is a functional renal failure due to low renal perfusion. Renal histology is normal or shows lesions that do not justify the decrease in glomerular filtration rate. The traditional concept is that hepatorenal syndrome is due to deterioration in circulatory function secondary to an intense vasodilation in the splanchnic circulation (peripheral arterial vasodilation hypothesis). Over the last decade, however, several features have suggested a much more complex pathogenesis. In this article new concepts on the pathogenesis of hepatorenal syndrome are reported, the current options for prophylaxis are shown, and the most applicable treatments are described.