Twelve children with alternating hemiplegia were treated with the calcium-entry blocker flunarizine for 4 months. All but one patient responded favourably with a reduction in frequency and/or duration and severity of attacks. Interictal symptoms decreased and mental development improved in several patients. Nine of the patients entered a subsequent double-blind placebo-controlled withdrawal study lasting another 4 months. Relapses were observed in part of the placebo as well as of the flunarizine-treated patients. The reason for this is not clear, since it is unlikely that the favourable response during the initial open-label study would be due to a placebo effect, or that tolerance to the drug had developed. Feed-back from the parents rather suggests that stress and tension, which were known trigger factors in a majority of these patients, played a role when the patient was switched to the double-blind treatment. Although the present study is not fully conclusive, apparently because of the use of an inadequate trial design, flunarizine, the first truly promising drug in this disease, deserves further study. An appeal is made to join another international double-blind study.