Human health risk assessment of disinfection by-products (DBPs) in drinking water was performed by using the water quality monitoring data. For probabilistic exposure assessment of DBPs about two waters, Monte-Carlo simulation is used. Exposure model included behavior of water drinking, food preparation, washing dishes, shower and bath in household. Han River water exceeded the standard of excess cancer risk (>10<SUP>-4</SUP>) on chloroform (CF) and bromodichloromethane (BDCM) about 50 percentile and 95 percentile value of exposure amount distribution, and exceeded the standard of hazard quotient (>1) on CF about 95 percentile value of exposure amount distribution. Nakdong River water exceeded the standard of excess cancer risk on CF and BDCM about 95 percentile value of exposure amount distribution, and exceeded the standard of hazard quotient on CF about 95 percentile value of exposure amount distribution. This means that there is no significant difference between the two waters, and ordinary daily use of drinking water of two waters in Korean household shows carcinogenic and non-carcinogenic hazard. Korea currently manages DBPs at the level below than the drinking water standard, but it is necessary to adjust the standard for DBPs of drinking water because the level of carcinogenic and non-carcinogenic hazard is concerned if drinking water is used throughout life.