Eleven pregnant squirrel monkeys were perorally exposed to lead during the latter two-thirds of pregnancy [mean blood lead 0.54 microgram/ml (2.61 mumol/l), range 0.39-0.82 microgram/ml (1.88-3.96 mumol/l)], at a dosing regime producing no maternal toxic symptoms. Lesions similar to lead encephalopathy and growth retardation of the fetal cerebrum were seen in some of the offspring, as well as neurological and behavioral symptoms at adult age. Cerebral lead levels in offspring (an abortion, stillborns, a sacrificed full-term fetus, and a neonatal death) were between 0.1-0.7 microgram/g. Pre- and perinatal mortality, and prematurity, was increased, and the size of the offspring at birth was reduced. The head circumference tended to be reduced postnatally. Zinc protoporphyrin in blood was determined in four of the pregnant monkeys; the mean values were between 0.58-1.05 micrograms/ml (0.93-1.68 mumol/l). These findings represent the first clearly prenatal brain damages described for experimental peroral lead exposure.