Analytical and quality control procedures are described for the determination of polychlorinated biphenyls in blood, adipose tissue, and milk from dosed female monkeys and their offspring, as part of a study to measure the toxicological effect of Aroclor 1254 on the pre- and postnatal development of fetus and infant, respectively. Recoveries of polychlorinated biphenyls from fortified blood, fat, and milk of monkeys ranged from 81 to 96%, whereas recoveries from fortified corn oil, used to evaluate routine analysis, ranged from 94 to 108%. The coefficient of variation for triplicate analyses of lipids and polychlorinated biphenyls in blood or adipose tissue or both was less than 10%. Polychlorinated biphenyl levels in blood, milk, and fat rose with increasing dosage. After weaning, when the infants were no longer exposed to polychlorinated biphenyls, their blood levels declined rapidly and approached maternal levels within 40 50 weeks. Approximately 100 weeks after weaning, polychlorinated biphenyl levels in adipose tissue of infants from treated dams reached the background levels of those in the control group. © 1994 Oxford University Press. All rights reserved.