Objective: To investigate the association between arsenic concentration in mother's hair and some neuro-behaviour signs of children. Subject and method: 438 children aged 6-14 years old of a province in northern Vietnam and her mother participated took part in this study. Exposed group was defined as households with arsenic in water tests 0.05 mg/l (212 children). The household had arsenic in water tests 0.01 mg/l (226 children) were considered non-exposed group). To investigate neuro-behaviour signs in children by asking their parents following Development Behavior Checklist - Parent (DBC-P) and to determine arsenic concentration in mother's hair. Result: The average arsenic concentration in mother's hair in exposed group was 0.48 +/- 0.37 ppm (0.01 ppm - 1.56ppm), higher than that among non-exposed group (0.19 +/- 0.15 ppm) (0.01 ppm - 0.85ppm) (p0.001). There were no differences arsenic concentration in mother's hair between boy-child group and girl-child group as well as arsenic concentration in mother's hair between each aged group (p0.05). There were an association between the arsenic concentration in mother's hair and some neuro-behaviour signs of children such as: unable pay attention for long time, quickly bored, depressed when alone, impatient, anxiety, worry, puzzle, non-self confident. Conclusion: It's necessary to monitor an abnormal neuro-behaviour signs of children in exposed arsenic group in order to apply early solutions and appropriate intervention if necessary.