Recent work on ACTH receptors in adrenal cells and adipocytes is reviewed. It is suggested that ACTH acts on two types of receptor: an adenylate cyclase receptor and another one that helps to guide cAMP into the correct compartment. The introduction of the term holoreceptor to indicate a unit that is recognized by the hormone and is able to produce a measurable effect, and of the terms discriminator, transmitter and effector to indicate the functional subunits of the holoreceptor is suggested as a measure enhancing clarity and flexibility of communication in this very complex field.