This project was developed to investigate the usefulness of newborn nails for monitoring in utero drug exposure. Cocaine, benzoylecgonine, morphine, methadone, caffeine, nicotine, and cotinine were determined in nail samples from the first 3 months of life of 25 newborns abandoned immediately after birth (group 1) and of 33 babies born at the local maternity hospital whose families were recruited on a voluntary basis (group 2). All substances were measured by gas chromatography-mass spectrometry (detection limit: 0.025 ng/mg). Moreover, analytical results were compared with mothers' self-reported habits when the information was available. In group 1, 12 nails were found positive for caffeine and 13 for both nicotine and cotinine. Six samples tested cocaine- (range, median: 0.14-0.25, 0.175 ng/mg) and benzoylecgonine-positive (range, median: 0.12-0.20, 0.165 ng/mg). Both nicotine and cocaine were always retrieved together with their main metabolite. Morphine was found in four samples (range, median: 0.10-0.15, 0.125 ng/mg), methadone in five samples (range, median: 0.12-0.26, 0.170 ng/mg) that were found negative for all other compounds. In group 2, two samples tested positive for methadone (0.16, 0.17 ng/mg). The mothers self-report of the use of coffee always corresponded to caffeine positivity in the newborn nails (n=6), whereas six samples tested positive for nicotine and/or cotinine with a non-smoking mother. Sixteen out of the 33 samples of group 2 tested negative for all compounds. In conclusion, for the first time, results showed that, once that sample collection problems are solved, nails of the first period of life can be a very interesting indicator of in utero drug exposure.