After working on treatment organization in radiotherapy (bonnes pratiques organisationnelles en radiothérapie--action pilote MeaH 2003), the development of a security policy has become crucial. With the help of Air France consulting and the MeaH, three cancer centers in Angers, Lille et Villejuif worked together on the implantation of experience feed back committees (Crex) dedicated to the registration, analysis and correction of precursor events. This action has now been implemented in all the FNCLCC centers. It seems now important to have a program of mutualisation of corrective actions for all participants. This will allow to review the Orion method of events analysis.