Adrenergic receptors form the interface between the sympathetic nervous system and the cardiovascular system. Genomic or cDNA clones for 8 types of mammalian adrenergic receptors have been obtained. Much has been learned about the structure and functional properties of the beta-2-adrenergic receptor. Less is known about the functional properties and the physiologic role of the other adrenergic receptors. Further progress in this field may lead to the development of more selective drugs to modify the physiologic processes controlled by these receptors.