During the bombing of London in World War II, Bywaters and Beall described an acute loss of kidney function that occurred in severely injured crush victims (1). Acute tubular necrosis (ATN) was the term coined to describe this clinical entity, because of histological evidence for patchy necrosis of renal tubules at autopsy. In the clinical setting, the terms ATN and acute renal failure (ARF) are frequently used interchangeably. However, for the purposes of this review, the term ARF, rather than ATN, will be used. ARF will not include increases in blood urea due to reversible renal vasoconstriction (prerenal azotemia) or urinary tract obstruction (postrenal azotemia).