In 31 patients with at least 3 migraine attacks per month the prophylactic effect of tolfenamic acid 300 mg/day, propranolol 120 mg/day, and placebo was compared in a randomized doublè-blind cross-over study. The patients were treated for 12 weeks with each drug, but only the last 11 weeks were used for evaluation. Both tolfenamic acid and propranolol significantly reduced the number of attacks, the total duration of attacks and additional drugs taken when compared with placebo. Tolfenamic acid, but not propranolol, significantly reduced the median intensity of pain and the number of attacks confining the patients to their beds when compared with placebo. Only mild adverse reactions occurred with no significant difference between the drugs. It was concluded that the prophylactic effect of tolfenamic acid 300 mg/day in migraine was at least as good as propranolol 120 mg/day.