An efficient but little known tool for the application of the ALARA principle: ISOE (Information System on Occupational Exposure).The Information System on Occupational Exposure to ionizing radiation (ISOE) is a program launched by the Nuclear Energy Agency (NEA) in 1992. It was developed to address the needs of nuclear power plants and safety authorities as a comparison and information tool on practices in terms of optimization (ALARA principle), in NEA member countries. To date, more than 90% of the operating nuclear power plants in the world are participating in this program, which is organized in a decentralized form, with a steering group and four technical centers (Europe, Asia, north America and IAEA). The ISOE program includes an occupational exposure database and an information exchange and communication network. The databases permit the preparation of studies and comparisons of practices, either in a factual or analytical way. Thus, the ISOE program favors exchanges to the benefit of all participants and helps to bring operational radiation protection ever closer towards the "achievable" of ALARA.