Regardless of the many considerations, GR43175 has been shown to be effective when administered subcutaneously and orally as well as when administered intravenously in the treatment of acute migraine. It is now in phase III clinical trials and promises to provide a major breakthrough in migraine therapy. Importantly, further studies on its clinical mechanism of action are in progress and they will, it is hoped, be invaluable in elucidating the pathogenesis of migraine and vascular headache.