Sumatriptan is a serotonin1 (5-HT1) receptor agonist, which is effective in the acute treatment of migraine headache. Its antimigraine activity is believed to derive from selective vasoconstriction of cranial blood vessels which are dilated and distended during migraine headache and/or from inhibition of neurogenically mediated inflammation in the dura mater. In placebo-controlled comparative studies, sumatriptan reduced migraine headache from 'moderate or severe' to 'mild or none' within 2 hours in 50 to 73% of patients following oral administration of 100 or 200 mg, and within 1 hour in 70 to 80% of patients following subcutaneous doses of 6 to 8 mg or intranasal doses 20 mg into each nostril. In addition, sumatriptan alleviated the accompanying symptoms of nausea, vomiting, and photophobia/phonophobia more effectively than placebo, and permitted higher percentages of patients to resume normal daily activities. Sumatriptan 100 mg orally was more effective in the acute treatment of migraine than oral combination therapy consisting of ergotamine 2 mg plus caffeine 200 mg or aspirin 900 mg plus metoclopramide 10 mg. Pooled data from nearly 5000 patients treated with either oral or subcutaneous sumatriptan in clinical trials indicate that it is well tolerated. However, migraine recurrence within 24 or 48 hours of initial symptom resolution developed in approximately 40% of patients treated with sumatriptan, irrespective of route of administration. It is likely that migraine recurrence is related to the short half-life of the drug (approximately 2 hours). Future studies should attempt to ascertain whether additional doses of sumatriptan will help prevent migraine recurrence in patients with attacks of long duration and if so, should determine the optimum interval between dosages. In conclusion, sumatriptan is an important addition to the range of drugs currently available for acute treatment of migraine. It provides rapid relief from debilitating symptoms in a high percentage of patients, particularly after subcutaneous administration. At this stage in its development a number of questions remain to be answered - most notably whether repeat doses will help prevent recurrent attacks and which patients are most likely to respond to therapy. Nevertheless, sumatriptan presently offers a combination of efficacy and tolerability that is unique in this particular clinical setting.