This presentation will discuss about when laboratory researchers are or likely to be exposed to carcinogens. Researchers who work in chemistry R&D laboratories use various chemicals including carcinogens and epidemiological studies have reported the association between laboratory workers and excessive cancer mortalities. The nature, degree and duration of exposure to hazardous chemicals among laboratory workers should be determined in order to assess any risks and to protect laboratory workers’ health. Exposure assessment and characterization for laboratory workers, however, has not been properly addressed partly because the laboratory working conditions are unlike typical industrial settings, i.e., frequently changing tasks, multiple chemicals in use simultaneously, irregular work schedules, etc. Upon recognizing the significance of exposure assessment, Laboratory Safety Act in Korea has recently added legal requirements of performing exposure assessment of hazardous chemicals. A couple of topical studies will be introduced in this presentation: 1) case studies conducted in order to investigate how many and what kind of carcinogens are in use, 2) exposure characterization of volatile organic compounds (VOCs) in chemistry research laboratories.