One hundred and thirty-one male and female outpatients, aged 18-70 yr, with acute pain in the ankle joint caused by a post-traumatic sprain, entered a multicentre, randomised, double-blind, parallel-group, study. The patients were assigned to a 40 mg flurbiprofen patch (n = 65) or a non-medicated (but otherwise identical) control (n = 66), 12-hourly over 7 days, and were assessed at entry and after 3 and 7 days treatment. On day 7, spontaneous pain (the prime efficacy parameter), as evaluated by the patient on a visual analogue scale in the physician's office, showed significant improvement in the 40 mg flurbiprofen patch group compared to control (change from baseline) (p = 0.039), a result corroborated by the evaluation of the periarticular oedema: a reduction of 77.4% was observed in the 40 mg flurbiprofen patch group, compared with 63.8% in the control group (p = 0.025). The other selected efficacy criteria showed changes with a trend in favour of the 40 mg flurbiprofen patch but without statistical significance. Two mild and local adverse events were reported by two flurbiprofen patch patients, but neither patients discontinued the treatment prematurely. Physicians and patients found the flurbiprofen patch to be efficacious and well tolerated. Compliance was excellent in both groups. The efficacy and tolerability of the 40 mg flurbiprofen patch are therefore confirmed in the treatment of acute ankle sprains.