Methodology for health risk assessment has been developed by governmental agencies and research institutions in the United States concerning environmental and industrial health such as Environmental Protection Agency, Pood and Drug Administration, and Occupational Safety and Health Administration. The basic concept, process, and scientific rational of the health risk assessment are discussed in order to introduce this field of research for future application to risk assessment and management in Korea. As environmental criteria for most of the environmental carcinogens and nonfarcinogens are set based on the quantitative risk assessment, this quantitative methodology should be emphasized and studied in Korean situation.