Seven patients aged 13 to 17.5 years developed acute renal failure after treatment with a variety of non-steroidal anti-inflammatory drugs (NSAID): naproxen, diclofenac, ibuprofen, dipyrone and paracetamol. Six of the patients used more than one kind of NSAID. None of the patients had previous history of renal disease or concomitant treatment with other drugs. The time interval between NSAID administration to the emergence of symptoms ranged from 1 to 4 days. The most common presenting symptoms were flank pain (4 patients), abdominal pain (3 patients) and vomiting (3 patients). All patients had normal urine output. Microscopic hematuria and proteinuria were found in 5 patients and leukocyturia in 2. Serum creatinine ranged from 1.3 to 8.3 mg% at presentation. Kidney biopsy was performed in 3 patients and showed findings consistent with mild interstitial inflammation in 1 patient, and normal renal tissue in 2. All patients were treated with intravenous fluids, 1 received corticosteroids. Renal function completely normalized in all patients within 7 to 16 days.