Abstract: Instrumental neutron activation analysis (INAA) was used to measure the content of arsenic in segmented human hair samples, with and without treatment by arsenide. The results reveal that the contents of arsenic are higher in each segment of the arsenide-treated sample than those of untreated ones, with a peak value at the treated position. The results indicate that arsenide can infiltrate into hair by adsorption. Three certified reference materials were used for verification of the analytical results. The measured values are in agreement with the certified ones within uncertainty limits.