The contamination of drinking water supply is becoming an increasingly serious problem in Korea. In order to protect public health, there is a need to regulate drinking water pollutants. The purpose of this project, a national project for three years starting from 1992 to 1995, is to assess the health risk of pollutants in drinking water and recommend guidelines and management plans for maintaining good quality of drinking water. This study was conducted to monitor 80 species of chemicals including volatile organic compounds(VOCs), polycyclic aromatic hydrocarbons(PAHs), pesticides and metals in six major rivers and their distribution system for drinking water in Korea, and evaluate health risk due to exposure to these chemicals through four main steps of risk assessment in drinking water. In hazard identification, 80 species of chemicals were identified by the US EPA classification system. In their steps of exposure assessment, sampling of raw, treated and drinking water from the public water supply system have been conducted from 1993 to 1995, and 80 chemicals were analyzed. In dose-response assessment, cancer potencies, unit risk estimates and virtual safety doses of carcinogens were obtained by TOX-RISK, and reference doses and lifetime health advisories of noncarcinogens were calculated. Finally, in the risk characterization of detected chemicals, health risk due to exposure to carcinogens (weight of evidence, A or B) such as vinyl chloride, carbon tetrachloride, 1,2-dichloroethane, benzen, 1,1,1,2-tetrachloroethane, trihalomethanes(THMs), lead and arsenic of tap water in several cities exceeded 10−5 level. We suggest that non-regulated chemicals such as vinyl chloride, carbon tetrachloride and 1,2-dichloroethane should be monitored periodically and be regulated by the Drinking Water Management Act.