The effectiveness of metoprolol as a prophylactic treatment of migraine was investigated in double-blind comparative trials involving more than 500 patients. In two trials using a slow-release preparation and a dose of 200 mg per day, metoprolol proved significantly better than a placebo and as effective as propranolol 160 mg/day or flunarizine 10 mg/day. At the dose of 100 mg per day metoprolol was significantly more effective than clonidine and clomipramine and not different from a placebo, propranolol 80 mg/day or pizotifen 1.5 mg/day. It is concluded that metoprolol is useful as prophylactic treatment of migraine and ranks among the main drugs used for the same purpose, such as propranolol and pizotifen.