In a multi-centre double-blind cross-over trial using the double-placebo technique, 55 patients with rheumatoid arthritis were treated for 10 days for each trial drug with ketoprofen (200 mg/day) and ibuprofen (1200 mg/day). Both drugs induced a clinically and statistically significant improvement of all the symptoms studied, except for pain at night during ibuprofen administration. Ketoprofen displayed a therapeutic efficacy significantly superior to ibuprofen in five of the eight symptoms studied. Side-effects were recorded in 10 patients receiving ketoprofen (one patient withdrew because of heartburn) and in nine patients receiving ibuprofen.