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.