Abstract: Objective To evaluate the DNA damage in peripheral blood lymphocytes of individuals exposed to drink ing water arsenic.Methods Cometassay was used to evaluate the DNA damage in peripheral blood lymphocytes of 54 in dividuals with skin lesion and 51 without skin lesion.Urinary arsenic of all subjects were measured.The data on age,sex, smoking,alcohol drinking and history of pesticide exposure of all subject swere collected with a questionnaire.Results The results of the comet a ssay showed that the tail lengths of groups with and without skin lesions were 12.34±5.22 Lm and 7.35±3.67 Lm with a significant difference(P < 0.05).Urinary arsenic contents were 1.61±0.41 and 1.52±0.55 ng/1 000 gcrea tinine without significant difference(P > 0.05).Smoking and duration of using well were the risk factors of DNA damage.While the effects of a lcohol consumption on DNA damage was not observed.Conclusion Our study suggests that smoking and duration of using well are the risk factors of DNA damage.Comet assay can be used as a possible earlier index of the genetic damage of cell in arsenic exposed area.