This volume represents a collection of papers which were contributed by participants at a Symposium for Cholinergic Mechanisms and Psycho pharmacology, held in La Jolla, California on March 28-30, 1977. The were chosen to emphasize areas in which there has been substantial topics progress in the past 2-3 years and fall into seven major groups dealingwith: cholinergiC receptors; chemistry, histochemistry and enzymology; cyclic nucleotides and cholinergiC mechanisms; storage, compartmentation and release of acetylcholine; regulatory mechanisms in acetylcholine metab olism; modulation of acetylcholine metabolism; and behavioral and clin ical manifestations of cholinergiC function and dysfunction. Each group contains one or more reviews and a number of shorter contributions de scribing current work. This symposium was the third in a series of which the first two were held in Skokloster, Sweden in 1970 and Boldern, Switzerland in 1974. The Proceedings of the meetings indicate a rapid development of knowledge of cholinergiC mechanisms which for many years lagged behind that of other neurotransmitters and neuroregulators. The inclusion of a large section in the present volume dealing with clinical manifestations of cholinergiC dysfunction reflects one of the most important trends in current research on cholinergiC mechanisms, namely the close inter-relationship and mutual support of basic science and clinical investigation. I hope that this volume will be of value to all those whose work relates to cholinergiC function, at both basic and clinicalleve18, and will continue to stimulate the vigorous exchange of ideas which was such a prominent feature of the Symposium.