PRISMA-RT is an association between of seventeen radiotherapeutic institutions that have decided to cooperate in the field of patient safety. The association has been established on April 10, 2008. The name ‘PRISMA-RT’ is an acronym for Prevention, Recovery and Information System for Monitoring and Analysis in RadioTherapy. The well known PRISMA-analysis method has been developed by Tjerk van der Schaaf and is the basis for this cooperation. It is therefore integrated in the name of association.