To determine the renovascular effects of nonprescription ibuprofen in the maximum labeled over-the-counter (OTC) dosage for 7 days, and to compare these effects with those of two other available OTC analgesics, aspirin and acetaminophen, we evaluated 25 elderly patients with mild thiazide-treated hypertension and mild renal insufficiency. Under double-blind conditions, patients were randomly allocated to one of three treatment groups: ibuprofen 400 mg 3 times/day, aspirin 650 mg 3 times/day, or acetaminophen 650 mg 3 times/day. Blood pressure and indexes of renal function (blood urea nitrogen, creatinine clearance, serum electrolytes) were measured over 7 days in a clinical research center. None of the treatments had a clinically significant effect on blood pressure. Renal function indexes also remained unchanged during all three treatments. We conclude that elderly patients with mild thiazide-treated hypertension and mild renal insufficiency seem not to be at risk of developing additional renal compromise or of having their hypertension control diminished by treatment with these OTC analgesics for 7 days.