Abstract: An out-break of endemic arsenism occurred in certain areas in Xinjiang due to prolonged in take of well-water containing high arsenic content of 0.48-0.61 mg/L (normal permissible content being 0.04mg/L).Among 889 inhabitants with their age above 6 in 2 localities, 579 persons suffered from arsenism with a morbidity of 65.1%.The incidence varies in direct proportion with age: duration of taking well-water and amount of arsenic in well-water.