Eighteen postoperative surgical patients with acute renal failure were treated by hemodialysis. Trauma and operations for abdominal aortic vascular disease predominated as etiologic factors. Hypotension was the most common etiologic mechanism and occurred in 14 patients. In two cases kanamycin sulfate-treated sepsis preceded renal failure without hypotension. There was one case each of prolonged clamping of the aorta above the renal arteries and traumatic thrombosis of the aorta. There were 12 deaths, none of them attributable to failure of the dialysis method. Most deaths were due to sepsis, gastrointestinal tract bleeding, and acute pulmonary insufficiency.