Abstract. The European Fusion File (EFF) Project is a collaborative project with work funded by the European Fusion Development Agreement (EFDA). The emphasis is on the pooling of resources and removal of duplication of effort, leading to the efficient development of two types of nuclear data libraries for use in fusion power plant design and operation studies. The two branches consist of, on the one hand, a transport file for modelling and design capabilities and, secondly, an activation file for the calculation and simulation of dose rates and energy release during operation of a future power plant. The OECD Nuclear Energy Agency’s Data Bank acts as the central repository for the files and all information discussed during twice yearly meetings. It offers its services at no charge to the Project.