THE RECOGNITION of acute tubular necrosis (ATN) as a type of reversible renal failure and the use of extracorporeal or peritoneal dialysis (to excrete metabolic waste) during the regenerative stage of healing has reduced the mortality from this serious complication. The diagnosis and therapy of surgical patients with uremia and ATN differs in several important aspects from those patients without the superimposed catabolic stress and effects of operative trauma. This paper describes the diagnostic and therapeutic indices used in treatment of surgical patients with several types postoperative uremia and illustrates the methods available in supporting renal function during acute reversible insufficiency. Materials and Methods Fifty patients with the diagnosis of renal insufficiency associated with operative therapy were admitted to Barnes Hospital from 1960 to 1967. All patients treated had therapy directed by the renal division of the Department of Medicine conjointly with the Surgical Service. Ten patients with acute renal