In a report reviewing the 37 plenary talks and 80 poster sessions presented at a colloquium on Structure and Function of P2 Purinoceptors held by the American Society for Pharmacology and Experimental Therapeutics in 1995, a historical overview of the field, the molecular biology of P2 purinoceptors, signal transduction pathways of P2 purinoceptors, and a discussion of the physiological and pharmacological significance of P2 receptors in mediating diverse functions in a variety of tissue systems were presented. P2 Purinoceptors are plasma membrane receptors which are activated by extracellular nucleotides, and are divided into two types, G-protein coupled receptors and ligand gated ion channels. P2-Purinoceptors have been found to play important roles in the regulation of physiological processes. Recently, the discovery that nucleotides can be used as therapeutic agents in the treatment of cystic fibrosis, vasospasm, stress incontinence, diabetes, inflammatory disease, and cancer has sparked intense interest in the P2 purinoceptors. They have been classified by use of subtype selective agonists and antagonists and have been cloned and their cDNAs expressed in in-vitro systems. The authors express the opinion that future studies will be dependent on the availability of cDNAs for a wide variety of P2 purinoceptor subtypes which will facilitate the examination of the selective expression of these subtypes under the specific conditions relevant to physiological and pathophysiological states. In this way it will be possible to uncover the regulatory processes governing expression of the various P2 purinoceptor subtypes and discover how expression of these subtypes affects overall tissue physiology.