There are conflicting reports on the ability of aspirin as a single agent to cause acute or chronic renal failure in experimental animals. Chronic administration of aspirin alone over 18 to 68 weeks in doses of 120 to 500 mg/kg/d has been reported to cause renal papillary necrosis in rats. However, some investigators have been unable to produce renal papillary necrosis in other species or in rats given lower divided doses comparable to therapeutic doses used in humans. In a variety of rat strains, aspirin administered as a single high dose intravenously or by oral gavage produces acute tubular necrosis of proximal tubules, rarely accompanied by renal papillary necrosis in susceptible strains. Several human studies have addressed the chronic nephrotoxicity of aspirin alone or relative risk of end-stage renal disease in association with aspirin use after correction for other analgesics. With the exception of one case control study demonstrating a low, but statistically significant risk of end-stage renal disease in association with aspirin use, all other case control studies and several prospective studies have been unable to identify a significant risk of chronic renal failure in patients using aspirin alone in therapeutic doses. In healthy adults, short-term aspirin administration in therapeutic doses has no effect on creatinine clearance, urine volume, osmolar clearance, or sodium and potassium excretion. However, in predisposed individuals with glomerulonephritis, cirrhosis, and chronic renal insufficiency, and in children with congestive heart failure, short-term aspirin use in therapeutic doses may precipitate reversible acute renal failure. Acute aspirin intoxication (>300 mg/kg) frequently causes acute renal failure and doses of 500 mg/kg may be lethal. Chronic salicylate intoxication has been reported to cause reversible or irreversible acute renal failure in association with a pseudosepsis syndrome.