The European Space Agency (ESA) is engaged in the preparation and flight of a broad range of spacecraft, including for science, applications and manned missions. These are all susceptible to the effects of the space radiation environment. This susceptibility is increasing as the demands made of missions increase, both in terms of performance and in terms of reliability. Expanding manned activity in space also introduces the question of radiation hazard to humans. The principal elements of the radiation environment are described, along with their effects and with procedures adopted for evaluation and analysis of expected environments and effects. Problem areas identified include the need for updating radiation-belt models and the need for greatly expanded in-flight environment monitoring and technology demonstration.