The calcium-entry blocker flunarizine (Sibelium; Janssen) was compared with the beta-adrenoreceptor-blocking agent propranolol in the prophylaxis of migraine. Fifty-eight patients were entered into a double-blind 4-month treatment trial. Patients in whom beta-blockers were contraindicated were excluded from the trial. At the end of the trial 28 patients had received 10 mg flunarizine at night during the study, 29 patients had received 60 mg propranolol 3 times a day and 1 patient was withdrawn. Both groups responded well; and there was a 4-fold drop in frequency of attacks. There was no significant difference between the two groups in terms of patient profile, onset of response to therapy, final response to therapy, incidence of dropout from the trial or incidence of side-effects. Side-effects for flunarizine were weight gain (9 patients) and tiredness (6), and for propranolol sleep disturbances including nightmares (6), tiredness (8), mental changes (e.g. irritability) (3) and weight gain (4). Both flunarizine and propranolol are useful drugs for migraine prophylaxis and can be used effectively as first-line drugs. The low incidence of generally mild side-effects with flunarizine may make it preferable to many of the agents at present in use for migraine prophylaxis.