The pA2 value of several alpha 1-adrenoceptor antagonists on noradrenaline-induced contractions of rat aorta, and their affinity for the cloned alpha 1a-, alpha 1b- and alpha 1d-adrenoceptor subtypes were evaluated. Selective or moderately selective alpha 1d-, partially selective alpha 1b-, selective alpha 1a- and non subtype-selective alpha 1-adrenoceptors antagonists were included in the study. The potency of these compounds on rat aorta was well correlated with the affinity observed for the alpha 1d-adrenoceptor subtype. A poor correlation was found for the alpha 1b- and alpha 1a-subtypes. These results suggest that the alpha 1d-subtype plays a determining role in rat aorta contractions induced by noradrenaline.