Hepatorenal syndrome is a life-threatening complication of severe liver disease. It is generally accepted that the syndrome is the final stage of complex hemodynamic derangements associated with portal hypertension, ie, peripheral arterial vasodilation, effective hypovolemia, and hyperkinetic status. In spite of reduced systemic resistances, intrarenal vascular resistances are increased. This is probably the consequence of the activation of systemic vasoactive factors, such as the renin-angiotensin system, the sympathetic nervous system, and vasopressin aimed at restoring arterial filling pressure. Recently, it has been shown that intrarenal vasoconstrictors, such as leukotrienes and endothelins, are activated with the progression of liver disease. The renal vasoconstriction is counterbalanced by the intrarenal hyperproduction of vasodilating prostaglandins and kallikreins. When this balance is lost, for whatever mechanism, the renal vascular resistances dramatically increase and the hepatorenal syndrome develops. In spite of increased knowledge about pathogenesis, the treatment of hepatorenal syndrome remains unresolved. Low-dose dopamine or ornipressin are currently employed in many liver units to avoid further deterioration of renal function in patients with severe liver disease who are waiting for liver transplantation that remains, at present, the only effective treatment for hepatorenal syndrome.