We evaluated the sensitivity of 5-HT1D receptors in patients with migraine using sumatriptan as a pharmacological probe. The drug inhibits the release of ACTH, cortisol and prolactin and this effect may be used to explore the function of serotoninergic systems in vivo. We administered sumatriptan (6 mg sc) and placebo to 15 migraineurs, during the headache-free period, and to 10 healthy controls. Blood samples were collected -15, 0, 15, 30, 45, 60 and 90 min after injections. Sumatriptan induced a significant (p<0.01) decrease of ACTH, cortisol and prolactin concentrations both in patients with migraine and in controls. The neuroendocrine response was not significantly different in the two groups. Our results suggest that 5-HT1D receptor sensitivity is not altered in migraine.