Abstract: Objective In order to understand the association between the exposure to chlorinated water and risk of bladder cancer in Chongqing.Studies were made to accumulate data concerning epidemiological study on carcinoma caused by chlorinated water.Methods Case-control study of bladder cancer and exposure to chlorinated water was conducted from December of 1998 to 2000 October of in Chongqing area.The relevant factors in a total of 211 histological verified bladder cancer cases and 230 other cases controls which matched by age,sex and the years of residence in Chongqing were analyzed by com-parision.Subjects were interviewed with questionnaires and the data were analyzed with EPI 5.01 and SPSS software.Results The risk factors of bladder cancer were complex.Exposure to drinking water chlorination and chlorination by-products was risk factor of bladder cancer including smoking,wine,history of genetic,et al.Conclusion Exposure to chlorinated water may be a risk factor for bladder cancer in Chongqing.More epidemiology studies on the field would be carried out.