Sumatriptan is a new serotonin receptor agonist that is useful in the treatment of migraine headache. More than 70 percent of patients with migraine headaches respond to subcutaneous sumatriptan within two hours, although headaches recur in up to two-thirds of initial responders. Side effects include lightheadness, a sensation of tingling or warmth, and breathlessness. Compared with the combination of ergotamine and caffeine, sumatriptan appears to work earlier and more completely but is associated with a higher rate of recurrent headache. Sumatriptan may be a useful additional therapy for migraine headache.