ABSTRACT. - Nuclear Accidents and the Environment. Radiation emergencies can have severe effects on the enviornment and the people, who realize that nuclear danger and its associated problems can arise not only from nuclear incidents including accidents in nuclear power plants or research institutions, but also from low radiation exposure. In peacetime, accidents in nuclear power plants or research institutions dealing with radioactive materials can lead to overexposure of persons to ionizing radiation. The environmental and health response to a radiation emergency depends on its magnitude. The International Nuclear Event Scale (INES) is a scale that includes eight levels and assesses the severity of events at nuclear facilities. In the case of a nuclear accident, the level of radiation hazard for the environment and the people depends on the quantity and principle radionuclides released into the environment, the distance of the populated areas from the source of radioactive fallout, the type of buildings, meteorological conditions at the time of accident etc. The international community have agreed on several basic principles to mitigate the effects: protective actions for early or urgent response, including sheltering, evacuation and prophylactic use of iodine; and protective actions for later phases of response, including temporary relocation, permanent resettlement and control of water and food.