The review is organized into two major sections: Part I, a clinical review which will examine only those studies relevant to the issue of behavioral effects resulting from relatively low-level chronic exposure, and Part II, a review of animal studies which will focus on behavioral reports only; i.e. studies where the dependent variable is learning, performance, or some aspect of locomotor behavior. No attempt will be made to review the equally large animal literature dealing with physical development, neurochemical, electrophysiological, or neuropathological endpoints of toxicity.