Newborn rats of the albino Wistar strain were exposed to lead from birth to 20 days of age through mothers milk, from dams which were fed diets containing 0, 0.25, 0.5 or 1.0% powdered lead. Subsequent determination of tissue lead revealed a direct relationship between the lead levels in both blood and brain of the pups and the lead dosage to which they were indirectly exposed via the dams' milk. Lead retention in both tissues was still evident at 100 days of age, with the relative elevation of lead levels being an order of magnitude higher in brain than in blood. There were no obvious signs of lead intoxication in the pups, apart from mild growth retardation in the group with the highest lead burden. However there was a significant retardation in behavioral development observed on two of four measures which were employed. It was concluded that brief exposure to low lead levels in infancy can have long lasting consequences in the brain and in behavior.