Behavioral toxicological and clinopathological studies are in progress on infant monkeys treated with doses of lead chosen to produce subclinical effects. In the current grant year, new infant monkeys will be obtained from mothers carrying blood lead (PbB) burdens in the approximate range of 35-70 micron g/dl, and hence will have been exposed in utero to these levels. Some of these infants will be nursed by the mothers maintained on their leaded diets, and others will be nursery reared with comparable amounts of lead added to their nursery milk. These monkeys will continue to receive lead until the end of the first year of life, and will be tested behaviorally on locomotor activity, social behavior, and various discrimination tasks in the Wisconsin General Test Apparatus. In addition, monkeys exposed either in utero or postnatally to similar schedules of blood lead burdens in previous years, will be retested on similar tasks, to assess the persistence of earlier seen behavioral effects of lead or to determine if delayed or more exaggerated symptoms appear with neurobehavioral development (even though lead intake was discontinued in all these monkeys at one year of life).