Objectives. We assessed tobacco smoke exposure (TSE), defined according to detection of cotinine, in dried blood spots collected fromchildren for lead screening. Methods. Dried blood spots collected from a national sample of 1541 Black and White children and submitted to a commercial laboratory for lead analysis were analyzed for cotinine. We used an anonymous administrative data set including information on children's characteristics to conduct univariate and multivariate analyses. Results. Cotinine was detected in 61% of dried blood spots; 17% of samples had cotinine levels above 3 nanograms per gram. Median cotinine levels were significantly higher among Black than White children (0.66 ng/g vs 0.30 ng/g) and among Medicaid recipients (0.94 ng/g vs < 0.3 ng/g). In multivariate analyses, significant increases in cotinine levels were associated with Black (vs White) race, older age, Medicaid coverage, higher state smoking rate, and higher average winter temperature. Detectable cotinine levels were significantly associated with higher lead levels. Conclusions. TSE is highly prevalent among children undergoing lead screening, and exposure levels are greater among Black children and children on Medicaid. TSE may contribute to lead exposure. Concurrent lead screening and biological screening for TSE may be a feasible approach to increasing childhood TSE detection.