The conceptual process of drug discovery is one that is often the result of an identified need in a defined disease area. This need represents a mandate from the marketing department of a phar maceutical company or a breakthrough at the research level that has agreed applicability in response to a valid therapeutic demand. Although the intelligent design and development of new thera peutic entities, as evidenced by Sir James Black's H -receptor an 2 tagonist cimetidine (Tagamet), is intellectually satisfying, many novel drugs arise from serendipity, from the chance observation of the research scientist or the clinician, that a compound has unex pected actions of use for the treatment of human disease states. Drugs that have been identified by this route include the antipsy chotic chlorpromazine and the putative anxiolytic buspirone. The events surrounding the process of drug discovery and de velopment are the theme of the present volume, which attempts to present, in a logical and lucid manner, the complexity of a process that is often naively assumed to represent nothing more than the identification of a new compound and its rapid introduction into humans, free of such complications as efficacy, selectivity, safety, bioavailability, toxicity, and need.