Hepatorenal syndrome (HRS) represents functional renal failure in patients with liver insufficiency. HRS can appear spontaneously or can be the consequence of specific events. The most important triggers are bacterial infection, gastrointestinal bleeding and excessive paracentesis. Other causes of acute renal failure must be excluded. Therapy consists in treatment of the underlying liver disease as well as expansion of plasma volume, administration of vasoconstrictors and, if applicable, early liver transplantation. Without adequate treatment, patients with HRS have a poor prognosis: The median survival expectancy is around 14 days in type 1 HRS and 6 months in type 2. Prevention consists in reduction of triggers as well as early recognition and treatment of deteriorating renal function.