The MEAH, a French national agency working on health services organization, has led a two-year campaign on safety improvement in radiotherapy centers. The pilot project involved three voluntary French cancer centers in 2005 and 2006. Building on the results of this project, a roll-out campaign has been launched, involving more than 50 additional cancer centers from 2007 and on. This paper presents the results of experiences of these campaigns. Notably, the axes of improvement chosen by professionals, such as risk analysis or use of checklists are discussed.