BACKGROUND: : Maternal smoking during pregnancy is associated with adverse perinatal outcomes. In view of concerns about underreporting, benzo[a]pyrene (B[a]P)-DNA adducts could be used to provide information about long-term in utero exposure to smoking but have not previously been used with samples from neonates. This study aimed to verify whether B[a]P-DNA adducts could accurately assess tobacco smoke exposure during fetal life. The objectives were to correlate B[a]P-DNA adduct levels with active maternal and passive smoking and to determine the sensitivity and specificity of smoking and nonsmoking status by comparing neonatal B[a]P-DNA adduct levels with those of maternal self-reports. MATERIALS AND METHODS: : B[a]P-DNA adducts in neonatal buccal cell samples were determined by a competitive immunoassay. Three groups of neonates were constituted according to maternal self-reported smoking status during pregnancy: nonsmokers (n = 25; control group), 10 cigarettes per day (n = 21; S+ group). RESULTS: : The mean B[a]P-DNA adduct level rose significantly when comparing the controls with the S- and S+ groups. Maternal active smoking had the strongest effect on B[a]P-DNA adduct levels in neonates. A crossanalysis between B[a]P-DNA adduct levels and maternal self-reported levels revealed high sensitivity and specificity. CONCLUSIONS: : This preliminary study suggests that B[a]P-DNA adducts are reliable biomarkers for the screening of long-term in utero exposure to smoking and are accurate when compared with maternal self-reported levels of active smoking. Detection of B[a]P-DNA adducts in neonates could provide a useful, noninvasive tool in clinical risk assessment studies but would benefit from further confirmation with another validated biomarker.