A retrospective cohort study was conducted to investigate the relationship between drinking water contamination and risk of leukemia in human being. It was found that the leukemia incidence rate of group D who drank the tap-water from Donghu Lake was significantly higher than that of the groups C and H who drank the tap-water from Changjiang River and Hangjiang River, RR = 1.77, 95% CL = 1.36-2.30, P < 0.01. But the difference between group C and group H is not significant. By using the sex- age-strata analysis; trend and correlation analysis, the results showed that there was a significant positive correlation between the RR of incidence of leukemia and tap-water mutagenicity. It was also connected with pollution of halogenated hydrocarbons in drinking water.