PURPOSE/OBJECTIVE: A national incentive brought about the instauration of systematic clinical audits of all Belgian radiotherapy departments (n = 25) from 2011 to 2015 using the International Atomic Energy Agency QUATRO (Quality Improvement Quality Assurance Team for Radiation Oncology) methodology. The impact of these audits was evaluated and the emitted recommendations originating from the audit reports were analysed to identify areas of weakness on a national basis. METHOD: The QUATRO audits performed in each radiotherapy department gave rise to reports in which each department received a list of recommendations that it is free to implement. These audit reports were analyzed to identify common areas for which improvements were recommended. Moreover, questionnaires were sent to all departments in order to evaluate the overall usefulness of the recommendations as well as the relevancy and the actual impact of each individual recommendation. RESULTS: Of the 381 emitted recommendations, 34% concerned process optimization of which a quarter involved process improvement and protocol development. Twenty-seven percent of the recommendations concerned infrastructure of which one-third was related to the quality of the equipment or facility. Nineteen and 20% of recommendations addressed department organisational and staff issues respectively. When analysing the departments' feedback questionnaires, 54% of the departments evaluated the audits' recommendations as being very useful. Furthermore, 42.7% of the recommendations were found to be very relevant and 23.5% were deemed to have an important impact. CONCLUSION: This first round of audits in Belgium allowed for the identification of common areas for improvements of practice in radiation oncology departments, with a focus on process optimization and infrastructure elements. Similarly, the audits' emitted recommendations were globally deemed very relevant. Encouraged, by this analysis, a second cycle of audits has started in Belgium with a modified version of the QUATRO ...