Poisons are topics of multidisciplinary concern. The clinician and the pathologist are sensitive to instances of human poisoning. The laboratory researcher, whether pharmacologist, physiologist, or biochemist, is oriented toward molecular modes of poison action. Both clinician and researcher are eager to learn of poisons that can be used as therapeutic agents or methodological tools. This volume is an attempt to underscore the multidisciplinary charac- ter of neuropoisons. Six poisons of animal origin which are receiving considerable clinical and research attention are discussed. Each poison is presented first as a clinical entity, then as a topic of investigative research, and finally as an agent useful to the study of nerve function. Because no single volume on neuropoisons can be exhaustive, an attempt at balance is offered as compensation. Two snake venoms, two marine poisons, and two bacterial toxins are presented in detail. In the sequel to this volume, attention will be focused on representative neuro- poisons of plant origin.