The seventh Jerusalem Symposium has tried to penetrate into a field of research towards which the efforts of a large number of the most variegated modern techniques are conversing: molecular and quantum pharmacology. The hope to elucidate the mode of action of drugs, to establish correlations between the electronic and con formational structures of drugs and their mode of action and level of activity, to derive from these data the nature of the cellular receptors and an understanding of the interaction of the drugs with those receptors - is a strong stimulus to enlarge and deepen the research efforts with the ultimate view to rationalize the design of more efficient and more specific drugs. The Symposium represents an attempt to survey the progress made so far in this respect and the methods and efforts employed in order to arrive at even greater achievements. The presentation of this Symposium differs somewhat from that of the preceding ones. Owing to the political events which disturbed the peace in the Middle East and therefore the normal activities of commerce and industry in Israel at least temporarily, the printing and distribution of this volume were entrusted to the Reidel Publishing Company. We wish to thank them for their very efficient col1aboration and for all their efforts to publish this volume with a minimum delay.