Occupational Exposure Management at Nuclear Power Plants : Fourth ISOE European Symposium Lyon France 24 26 March 2004 The Information System on Occupational Exposure (ISOE) has become a unique worldwide programme on the protection of workers at nuclear power plants. It includes a vast network for exchanging experience in the area of occupational exposure management as well as the worlds largest database on occupational exposure from nuclear power plants. Each year an ISOE international symposium offers a forum for radiation protection professionals from the nuclear industry operating organisations and regulatory authorities to exchange information on practical experience with occupational radiation exposure issues in nuclear power plants. These proceedings summarise the presentations made at the 4 ISOE European Symposium on Occupational Exposure Management at Nuclear Power Plants held in March 2004 in Lyon France.