The role of vascular phenomena taking place during an attack of migraine are poorly understood. The aim of this study was to measure systemic levels of nitric oxide and endothelin-1, two of the most potent vasoactive mediators known, and to assess vasomotor responses through transcranial Doppler ultrasound monitoring in patients suffering from migraine without aura, both during the headache event and in headache-free periods as well as after pharmacologically induced pain relief. Seven patients (mean age 31.3 years, range 24 to 49 years), five women and two men, were enrolled in the pilot study. Transcranial Doppler recordings were performed according to conventional procedure. Endothelin-1 concentrations were measured by means of radioimmunoassay, whereas nitric oxide levels were estimated using electron paramagnetic resonance spectroscopy. Ultrasound evaluation did not show significant changes during migraine attacks compared to the interictal condition. Nitric oxide levels showed only slight differences between basal and attack conditions (0.85 ± 0.46 versus 1.56 ± 0.88, expressed as arbitrary units), and were raised after pharmacological intervention (2.91 ± 1.93, P<0.05). Plasma endothelin-1 concentrations decreased during migraine attacks with respect to interictal conditions (3.99 ± 1.21 pg/mL versus 4.23 ± 1.19), and returned to basal values (4.44 ± 1.08 pg/mL) after relief of pain. Coupling the measurements of systemic levels of nitric oxide and endothelin-1 with transcranial Doppler velocity results will provide useful information on the hemodynamic changes of cerebral blood flow regulation in migraineurs, thereby adding new insights into the mechanisms of the migraine attack.