A series of 10 cases with thymic tumor treated at the Institut Bordet were reviewed to assess the effectiveness of radiotherapy. Radiotherapy associated or not to an incomplete surgical resection yielded 3 cases of 5 year survival for invasive thymomas out of 5 patients with this follow-up. A review of the literature shows that irradiation at efficient doses will control local growth and improve survival in patients with invasive thymoma.