The purpose of these volumes is to provide a reference work for the methods of purifying many of the receptors we know about. This be­ comes increasingly important as full-length receptors are overexpressed in bacteria or in insect cell systems. A major problem for abundantly expressed proteins will be their purification. In addition to purification protocols, many other details can be found concerning an individual receptor that may not be available in standard texts or monographs. No book of this type is available as a compendium of purification procedures. Receptor Purification provides protocols for the purification of a wide variety of receptors. These include receptors that bind: neurotransmit­ ters, polypeptide hormones, steroid hormones, and ligands for related members of the steroid supergene family and others, including receptors involved in bacterial motion. The text of this information is substantial, so as to require its publication in two volumes. Consequently, a division was made by grouping receptors by the nature of their ligands. Thus, in Volume One there are contributions on serotonin receptors, adrenergic receptors, the purification of GTP-binding proteins, opioid receptors, neurotensin receptor, luteinizing hormone receptor, human chorionic gonadotropin receptor, follicle stimulating hormone receptor, thyro­ tropin receptor, prolactin receptor, epidermal growth factor receptor, platelet derived growth factor receptor, colony stimulating factor recep­ tor, insulin-like growth factor receptors, insulin receptor, fibronectin receptor, interferon receptor, and the cholecystokinin receptor.