During a one-year period, drug-associated acute renal failure (ARF) was prospectively recorded in 398 patients, registered in 58 french nephrology Units. Drugs involved were primarily antibiotics, mainly aminoglycosides, glafenine, non-steroidal antiinflammatory drugs and contrast media. Hypersensitivity reactions were reported in 69 patients. Renal biopsy, performed in 81 instances, showed acute tubular necrosis in 42 and acute interstitial nephritis in 20 patients. Hypotension, sodium depletion and/or cardiac failure were predisposing factors in 198 cases. Fifty patients died, 251 recovered fully or regained previous renal function, and in 93 permanent renal damage remained. Advanced age, oliguria, severe ARF, and preexisting cardiac, hepatic or renal insufficiency were poor prognostic factors. Prevention of drug-associated ARF should be directed to high-risk patients, particularly those receiving aminoglycosides and contrast media.