During the last decade much evidence has accumulated that supports the concept that in addition to the classical postsynaptic α₁-adrenoceptors that mediate the responses of effector organs to norepinephrine, there are also α₂-receptors located presynaptically on noradrenergic nerve terminals. These receptors are part of a negative feedback mechanism that modulates the release of norepinephrine in the periphery and the central nervous system. More generally, these α₂-receptors can be differentiated from the α₁-receptor by their specificity toward a series of agonists and antagonists. This pharmacological classification is independent of anatomical distribution. Such a subclassification of α-adrenoceptors opens new possibilities for drug discovery through the development of agonists or antagonists having a high degree of selectivity for each receptor subtype. We report here the synthesis and preliminary characterization of a novel and selective α₂-antagonist, 6-chloro-2,3,4,5-tetrahydro-3-methyl-1H-3-benzazepine (SK&F 86466).