Recent research has introduced into α-adrenoceptor pharmacology some interesting new aspects. In this article the presynaptic α-autoreceptors of noradrenergic neurones, and the subclassification of α-adrenoceptors into α1- and α2-types, are discussed. Presynaptic a-receptors occur at all noradrenergic axons where they have been sought. They subserve an autoinhibition in which released noradrenaline inhibits its own further release, and they are probably located on the terminal noradrenergic axons. It soon became clear that presynaptic α-receptors differed from classical postsynaptic a-receptors in their sensitivity to drugs. This led to a general pharmacological subclassification. α1-Adrenoceptors are the classical postsynaptic α-receptors of smooth muscle cells, but occur also elsewhere, e.g., in brain and liver. The prototypes of the α2-adrenoceptors are the presynaptic α-receptors, but similar receptors have since been identified outside terminal noradrenergic axons. For instance, in cholinergic neurones, α2-receptors mediate inhibition of acetylcholine release. The most unforeseen α2-adrenoceptors have recently been detected in smooth muscle cells, where, like the α1-receptors, they mediate contraction. The α1/α2 subclassification may have clinical implications, e.g., in the treatment of hypertension with α2-selective agonists and α1-selective antagonists.