The Radiation and Environmental Health (RAD) Unit of WHO/HQ evaluates health risks to environmental and occupational radiation exposure. The programs promote radiation researches, provide advice on emergency medical and public health responses to radiation accidents, and advice national authorities on how to minimize any risk to human health. This paper discusses the scope and structure of the WHO/HQ RAD Unit and identifies areas for the establishment of future joint projects within the framework of the 21st Century Center of Excellence (COE) programs of Nagasaki University, "International Consortium for Medical Care of Hibakusha and Radiation Life Science".