The goal of the application is to evaluate the effects of inadequate zinc intakes on biobehavioral development in early childhood. To do so, we will utilize a randomized controlled design, after zinc intakes via supplementation) and measure the aspects of the cognitive, sensorimotor and behavioral development of a cohort of infants, 6 to 18 months of age. We propose to conduct this research in Peru, where usual dietary intake of zinc is low, and where previous research findings support improvements in morbidity, growth and development associated with zinc supplementation. The specific aims are: 1) to evaluate dimensions of cognitive development (visual attention, executive processing and vigilance) in Peruvian infants at 6, 9, 12, and 18 months of age by supplement type; 2) To evaluate the sensorimotor and behavioral development of Peruvian infants at 6, 9, 12, 15 and 18 months of age through observations and maternal reports by supplement type. To accomplish the goal, 300 6-month old Peruvian infants will be randomized in a double-blind fashion to receive daily supplements containing 10 mg iron and 1 mg copper with or without 10 mg zinc until their 18- month birthday. Indicators of zinc, iron and copper status will be assessed at 6, 12, and 18 months of age. At 6, 9, 12 and 18 months of age, cognitive tests of visual attention (with concurrent heart rate monitoring), novelty preference, executive processing and vigilance, as well as measures of sensorimotor development BSID) will be conducted at the clinic. Four-hr event- (feeding, exploration) and timed- (every 5 min) sampling observations in the household will describe activity, behavior and infant interaction. Socioeconomic status, dietary intake, growth and morbidity will also be characterized. The study will yield new information on the role of zinc in the biobehavioral development of pre-verbal infants. Strengths of the study include the experimental design, the innovative methods proposed to measure cognitive development, and the uniqueness of the study site.