Study Abstract: The optimal management of renal replacement therapy (RRT) in acute renal failure (ARF) is uncertain. The VA/NIH Acute Renal Failure Trial Network (ATN Study) is designed to test the hypothesis that a strategy of intensive renal support will decrease mortality in critically ill patients with ARF as compared to less intensive (conventionally recommended) management. In this multicenter, prospective trial, patients with ARF due to acute tubular necrosis will be randomized equally to intensive or conventional management strategies for RRT.