Many Japanese today are suffering from health disorders related to their living environment, such as allergies and hypersensitivity to chemical substances. The Sick House/Building Syndrome has been a serious problem since 1996, due to low level exposure to hazardous chemicals such as formaldehyde and volatile organic compounds (VOCs) emitted in airtight houses. This paper aims to show current status of the syndrome in Japan and practical researches to promote prevention of, and improvement to indoor air pollution due to chemicals.