In a double-blind, cross-over multicentre trial, the prophylactic antimigraine effect of the beta 1-selective beta-blocker metoprolol was evaluated and compared with that of the non-selective beta-blocker propranolol. Metoprolol was used in a dosage of 50 mg b.i.d. and propranolol in 40 mg b.i.d. 56 patients with classical or common migraine were included in the double-blind part of the investigation. 3 patients withdrew, but none because of side-effects. The data suggest that metoprolol is clinically equivalent in effectiveness to propranolol in migraine prophylaxis regarding parameters such as attack frequency, improvement in sum of severity score and subjective evaluation. Both drugs were generally well tolerated and the number of reported side-effects was similar to those reported during the run-in period (placebo).