Each nuclear power plant, fuel cycle facility and nuclear research and test facility that is operating today will eventually reach the end of its useful life and cease operation. During the period of its decommissioning, it is important to properly manage the health and environmental hazards and physical protection measures of the shutdown facility in order to protect the health and safety of the public and workers and to safeguard any nuclear materials. In this regard, the nuclear safety regulatory body is responsible for independently assuring that decommissioning activities are conducted safely, that radioactive materials and spent nuclear fuel are disposed of properly and that the site is in an acceptable end state. The purpose of this report is to describe the broad range of safety, environmental, organisational, human factors and public policy issues that may arise during the decommissioning of nuclear reactors and that the regulatory body should be prepared to deal with in the framework of its national regulatory system. The intended audience is primarily nuclear regulators, although the information and ideas may also be of interest to government authorities, environmental regulators, nuclear operating organisations, technical expert organisations and the general public.<!-- -->