Hair samples were collected at time of delivery from 40 neonates whose mothers were known to be smokers during the prenatal period. Hair was decontaminated in dichloromethane, homogenized in NaOH, and nicotine was extracted in diethyl ether. After separation on a BP-5 capillary column, nicotine was identified and quantified by GC/MS using selected ion monitoring. In all cases, nicotine was found in the neonatal hair and in the hair of the corresponding mother. The ranges of nicotine levels were 0.15 to 11.80 ng/mg, and 0.37 to 63.50 ng/mg, for the neonates, and their mothers, respectively. It was possible to establish a significant correlation between both concentrations, and the correlation coefficient was 0.83. These findings suggest the possibility of monitoring the transfer of maternal nicotine through the placenta by measuring nicotine concentration in neonatal hair.