The hepatorenal syndrome is defined as the spontaneous onset of progressive renal failure in patients with far advanced hepatic disease, usually on the basis of cirrhosis. The clinical characteristics of the syndrome include azotemia, oliguria, hyponatremia, low urinary sodium excretion and the absence of abnormal findings in the urinary sediment. Although the results of a large number of studies suggest that abnormal histologic features in the kidneys are infrequent, changes such as glomerulosclerosis, degeneration of tubular cells and alterations in the basement membranes have been described. Theories on the pathophysiologic aspects of the syndrome, including reduced plasma volume, inferior vena cava hypertension and active renal vasoconstriction, are presented. The last of these is currently the most widely accepted theory in which there is a selective redistribution of blood flow away from the cortical nephrons to the medullary nephrons on the basis of selective cortical vasoconstriction. The role of the synpathetic nervous system, as well as that of plasma renins in the cause of this condition is explored. Therapy for the hepatorenal syndrome generally has failed to ameliorate extremely unfavorable mortality rates. Such factors as the effects of plasma volume expansion; various pharmacologic agents, including dopamine, Octopressin and metaraminol; portacaval shunt; transplantation of the liver, and steroids are discussed. Regardless of specific therapy, the few patients who do survive tend to demonstrate a significant reversible component with respect to hepatic disease.