One of the major advances in the understanding of the mechanism of action of hormones, neurotransmitters and drugs had arisen from the hypothesis that the physiological or pharmacological responses are trig- gered by their interaction with specific cell compo- nents, termed receptors. However, the presence of receptors has been inferred from indirect data, and only recently has it been possible to study the kinetics of the interaction between drug and receptors directly, through the so called "binding technique. " This NATO-ASI on "Principles and Methods in Receptor Binding" was devoted...