1. The hepatorenal syndrome is the development of renal failure in patients with severe liver disease in the absence of any identifiable renal pathology. 2. Decreased glomerular filtration is caused by a reduction in both renal blood flow and the renal filtration fraction. These changes arise as a consequence of a fall in mean arterial pressure due to systemic vasodilatation, activation of the sympathetic nervous system causing renal vasoconstriction, and increased synthesis of several vasoactive mediators, which together modulate both renal blood flow and the glomerular capillary ultrafiltration coefficient, and thence filtration fraction. 3. Patients with liver disease developing renal failure should have hypovolaemia excluded by volume challenge, and all nephrotoxic drugs including diuretics should be stopped. Broad-spectrum antibiotics should be given for subclinical infection, which may be a treatable precipitant of renal failure in cirrhosis. Renal perfusion should be optimized by ensuring that the blood pressure and systemic haemodynamics are adequate, and that if renal venous pressure is elevated, due to tense ascites, it is alleviated. 4. The prognosis of hepatorenal syndrome is poor with a > 90% mortality. However, patients can and do recover from the hepatorenal syndrome, but only if there is a significant improvement of their liver function, or if they undergo liver transplantation.