Renal failure in cirrhosis poses unique diagnostic and therapeutic challenges. Laboratory values and predictive equations grossly overestimate renal function in patients with cirrhosis. Development of renal failure connotes a worse prognosis; mortality is especially high with hepatorenal syndrome. Classification of the causes of renal failure in patients with cirrhosis is provided with more extensive discussion of selected causes. Finally, a suggested diagnostic approach to renal failure in cirrhosis is given.