['Maternal cigarette smoking, alcohol use, and other factors confound studies of in utero cocaine exposure. Our goal was to determine whether in utero cocaine exposure is associated with an abnormal neurologic examination in infants, while controlling for concomitant cigarette smoke exposure and other confounding variables.', 'Healthy newborns with birth weights > or =2000 g were prospectively enrolled into a race-matched study of cocaine-exposed and cocaine-unexposed infants. Urine and meconium samples were analyzed for illicit drugs, the cocaine metabolite, benzoylecgonine, and the nicotine metabolite, cotinine. A detailed neurological examination was performed at approximately 6 weeks of age by an examiner blinded to history.', 'At 6 weeks of age, 40 cocaine-exposed infants and 56 cocaine-unexposed infants were examined. Tone abnormalities were the only neurologic abnormalities discovered, predominantly generalized hypertonia. Logistic models found that maternal urine cotinine levels were predictive of an abnormal neurologic examination, whereas cocaine exposure or benzoylecgonine levels were not. No interaction was found between maternal cigarette smoking and cocaine exposure. Race, ethanol exposure, prenatal care, homelessness, and head circumference were not predictive of an abnormal tone examination. The odds ratio for an abnormal examination was 2.9 (95% confidence interval: 1.04-8.25), if the maternal urine cotinine level was >200 ng/mL.'] Are tone abnormalities associated with maternal cigarette smoking during pregnancy in in utero cocaine-exposed infants?