Nonsteroidal anti-inflammatory drugs predispose to acute renal failure in conditions associated with decreased RBF. Such conditions include advanced age, hypertension, chronic renal insufficiency, diuretic use, and any condition decreasing effective circulating volume. Strenuous exercise also causes marked reductions in RBF. The patient discussed developed severe acute renal failure after strenuous exercise and therapeutic doses of ibuprofen and hydrochlorothiazide-triamterene. Urinalysis showed a nephritic sediment with red blood cell casts. Renal biopsy showed acute tubular necrosis and arteriolar nephrosclerosis. Although exercise-associated acute renal failure is uncommon, susceptible patients with exercise-induced renal ischemia and prostaglandin inhibition may develop this complication.