Abstract: The concentrations of 23 elements in hair of serious and minor endemic arsenism patients are determined by NAA.A comparison of the elemental contents between these two groups is made by means of statistical t-test and also is compared with those from normal control group,i,e,the male adults) living in Beijing area.The results show that the highest content of As,Fe,REE,Ba,Br,Sb is found in serious endemic arsenism group,while the lowest conent of these elements is found in normal control group.But the highest content of Se,Ca is found in normal control group.There are extremely significant differences in content of above mentioned elements between the three groups (P<0.05 or P<0.001)The higher As content in hair,the more serious the patient's condition is.It seems that element Fe,REE,Ba etc may aggravate the arsenism,but element Se,Ca and Co may alleviate it.