Forty patients with rheumatoid arthritis and upper gastrointestinal lesions due to non-steroidal anti-inflammatory drugs entered a prospective 6-month double-blind placebo controlled study of dietary supplementation with gamma-linolenic acid 540 mg/day. Nineteen patients received active therapy (as evening primrose oil 6 g/day) and 21 received placebo (olive oil 6 g/day). No patient stopped non-steroidal anti-inflammatory therapy but three patients in each group reduced their dose. Other results showed a significant reduction in morning stiffness with gamma-linolenic acid at 3 months and reduction in pain and articular index at 6 months with olive oil. Whilst gamma-linolenic acid may produce mild improvement in rheumatoid arthritis, olive oil may itself have hitherto unrecognized benefits.