This paper describes the vascular effects of almotriptan in comparison with sumatriptan in human vessels and tissues in vitro. The contractile properties of almotriptan and sumatriptan were evaluated in vitro in the following arteries: meningeal, temporal, basilar, internal carotid, ophthalmic, pulmonary and coronary. In addition, the effects of almotriptan on the pulmonary vein and on bronchial tissues were studied. Almotriptan showed selectivity of action for migraine-related arteries (i.e. contractile EC(50) of 30 and 700 nm for meningeal and temporal arteries, respectively), whereas the effect on arteries supplying blood to the brain was lower. The contractile effect of almotriptan was lower than that of sumatriptan in pulmonary arteries, whereas in bronchial preparations no clinically relevant contractile responses were observed for either almotriptan or sumatriptan. In ophthalmic arteries the contractile effects of almotriptan and sumatriptan were similar, whereas lower contractile effects were obtained with almotriptan than with sumatriptan in coronary arteries.