In this study, the occurrence of trihalomethanes (THMs) of the tap water in Izmir City was investigated and the lifetime cancer risk of THMs through oral ingestion, dermal absorption, and inhalation exposure were estimated. The total THMs in samples taken from the Tahtali and Ball;ova Water Treatment Plants (TWTP, BWTP), which are the major water sources of the Izmir City were about 72 and 88 mu g/L, respectively. Chloroform existed at the highest concentrations in samples. Although the cancer risk evaluation of CHBr3 through oral route for both sexes was below the EPA level, the highest lifetime cancer risk was originating due to CHCl2Br; 5.2 x 10(-5) and 4.3 x 10(-5) for males and 4.76 x 10(-5) and 5.8 x 10(-5) for females, for the samples from BWTP and TWTP, respectively. While overall the average lifetime cancer risks through oral route, dermal absorption, and inhalation exposure for THMs were higher than the EPA acceptable risk of 10(-6) by about 87, 340, and 5.7 times in the samples from TWTP and 99, 390, and 7.9 times in the samples from BWTP, respectively. The average lifetime cancer risk for THMs in both sources was in decreasing order, CHCl2Br, CHCl2Br, CHCL3, and CHBr3 for both sexes.