[en] The Japanese nuclear emergency plan and preparedness has been reinforced on the basis of lessons learned from the accident at the Three Mile Island-2 nuclear power plant in March 1079 and the Chernobyl accident in 1986. The framework for measures against a nuclear emergency, currently in place is briefly presented. In Japan, the responsibility for the population's protection in case of accidents lies upon prefectural governments. The national government is providing financial and technical support to prefectural governments. To facilitate the technical support for emergency situations, a significant effort has been made to develop computerized support systems: a radiological dose prediction code system SPEEDI and an accident evaluation code COSTA. This enables the prefectural governments to prepare their local emergency response systems by establishing communication networks, emergency medical treatment organizations and radiation monitoring schemes, and also nuclear emergency education, training and exercises. 2 tab., 2 figs., 2 refs