Postpartum scalp hair samples from 82 term-pregnancy mother/ neonate pairs were analyzed for their concentrations of zinc (Zn), copper (Cu), cadmium (Cd), and lead (Pb), using inductively coupled plasma-mass spectrometry. Maternal and neonatal Zn concentrations had geometric means (and 99% confidence intervals) of 122.5 microg/g (117.9--131.5 microg/g) and 146.9 microg (141.5--156.7 microg/g) respectively. Corresponding Cu values were 18.4 microg/g (17.6--23.8 microg/g) and 6.7 microg/g (6.3--7.6 microg/g). Those of Cd were 0.49 microg/g (0.47--0.69 microg/g) in the mothers and 0.57 microg/g (0.55--0.86 microg/g) in the neonates. For Pb, they were 7.95 microg/g (7.60--9.32 microg/g) and 4.56 microg/g (4.39--5.56 microg/g). Cigarette smoking, despite its relatively low prevalence (19.5%), was associated with lower Zn and higher Cd and Pb concentrations and in lower Zn/Cd and Zn/Pb molar concentration ratios. Smoking also altered interelemental relationships, particularly those of Zn with Cd and Pb and those between Cd and Pb. Smoking frequency appeared to show negative dose-response effects on maternal and neonatal Zn concentrations, Zn/Pb molar concentration ratios, and birth weight. Mothers with a history of oral contraceptive (OC) usage had significantly higher Cu concentrations and lower Zn/Cu molar concentration ratios than non users, with the highest Cu concentrations and lowest Zn/Cu values being associated with third-generation OCs. No similar effects were elicited in the respective neonatal Cu concentrations. Neither alcohol consumption nor prenatal supplementation with iron and/or folic acid had discernible effects on the maternal or neonatal elemental concentrations. The data from this study suggest that in a given population of term-pregnancy mothers and neonates, significant interindividual variations in hair trace element concentrations can occur, irrespective of commonality of general environment, and that lifestyle factors, including cigarette smoking and OC usage history, can be significant contributory factors to such variations. The data are discussed in relation to the effects of smoking-associated exposure to Cd and Pb exposure on Zn availability for placental transfer, as well as on the quantitative maternal Zn supply levels to the fetus resulting from the known tendency of smokers to have lower dietary intakes of Zn.