1 The pharmacokinetic and clinical effects of concurrent oral indomethacin and frusemide administration were determined in eight patients with rheumatoid arthritis. 2 Oral frusemide significantly reduces the plasma level of indomethacin following concurrent administration of the two drugs orally. 3 A profile of pain index, articular index and grip strength following oral indomethacin (50 mg) was determined and although the decrease in articular index was less when frusemide and indomethacin were given together it did not reach statistical significance.