AbstractReceptors that mediate their effects through G proteins are predicted to have a seven transmembrane domain architecture. The last few years have seen a remarkable increase in the cloning of members of this superfamily leading to the identification of many more receptors than previously thought to exist on the basis of differences in agonist and antagonist specificities. This has important implications for nomenclature and classification, especially in view of the difficulty in relating receptors identified through cloning techniques to endogenously expressed receptors. Receptor cloning has also identified important differences in receptors between species raising the question as to whether these should be considered as species homologues or distinct subtypes. It is also becoming increasingly apparent that the pharmacology of this superfamily of receptors is influenced by the nature of the G protein present in the host cell and by alternative splicing of the receptor. The rapid pace of developments in this area necessitate the need for a regular publication summarizing recent developments. In the future, the cloning of G protein-coupled receptors will enable rationalization of the naming of individual receptor subtypes and identification of their inter-relationships.