Acute renal failure (ARF) complicates the clinical course of as many as 5% of all hospitalized patients with the critically ill and injured disproportionably at risk. Considerable effort has been expended to develop techniques to prevent ARF or to facilitate its resolution. However, to date, studies have failed to demonstrate that drugs can prevent onset or deterioration of renal function in the critically ill, and some studies have even suggested harm. Recent data suggest that NAC can reduce the incidence of ARF secondary to radio-contrast agents and improved techniques for RRT and, perhaps, new drugs aimed at improving cellular repair, will improve outcome from ARF in the future.