The onset of renal failure in a patient with cirrhosis or acute liver failure is alarming because it raises the possibility of the hepatorenal syndrome (HRS). Periodic surveillance of renal function is helpful in patients with severe liver disease to detect HRS early and to help correct reversible contributing factors. Once established, HRS responds relatively poorly to medical management, although recent advances have brought hope for an improved prognosis. In this article the diagnosis, pathophysiology, and management of HRS are discussed in detail, with an emphasis on recent diagnostic and therapeutic advances.