This multicenter retrospective study included 56 cases of histologically reviewed invasive epithelial thymic tumors. All these patients underwent surgical treatment or exploration and were referred for complementary radiotherapy. The majority received a dose higher than 4000 rad. Twenty-three out of 50 patients (46%) with incomplete resection received some chemotherapy. The local recurrence rate at 2 yr was 34%. The overall 5-yr actuarial survival was 46%. There was no evidence of any relationship between radiation dose and local control. No difference in survival was observed with or without chemotherapy, nor according to histological type or lymphocytic infiltration, except cases with very undifferentiated carcinomas which presented a worse prognosis. Nor was any difference in survival observed between patients benefiting from incomplete resection and those only having undergone exploratory thoracotomy and biopsy. Radiotherapy seems to decrease the rate of local recurrence in invasive carcinoma of the thymus. The role of chemotherapy is still debatable, but it could have a role in decreasing tumor volume before radiotherapy. This study has shown the necessity of histological review by a panel of histopathologists in an attempt to better define terminology and diagnosis. A prospective study is necessary in order to solve the problems of concepts and management in epithelial thymic tumors.