As early as in 1982, the European Organisation for Research and Treatment of Cancer Radiotherapy Group established a quality assurance programme. In the course of 20 years, quality assurance procedures have become a vast and important part of the activities of the group. Today, the membership committee uses standard procedures based on minimal requirements to evaluate current members and new membership applications. Moreover, for every new trial, specific quality assurance procedures are an integral part of the preparation of the protocol and executed under the responsibility of the study coordinator. With the growing complexity of the radiotherapy techniques used in the framework of the more recent trials, quality assurance procedures have also become more complex including trial specific phantom based measurements. Future ways to evaluate all steps of the radiotherapy process using a common platform connecting all users with the internet are currently under development. © 2005 Elsevier Ltd. All rights reserved.