One hundred and twenty-three cases with primary thymoma have undergone an operation from 1972. Sixteen elderly patients (over 70 years old) were compared with 107 young patients in clinical appearance, pathological findings and outcome. There were no differences in Masaoka's classification, World Health Organization (WHO) pathological classification and frequency of complications as myasthenia gravis in both groups. In elderly patients different kinds of neoplasms often occurred during follow-up periods compared to in young patients. In both groups, basically policy of treatment is same. In the case of stage I or II, (extended) thymothymomectomy is performed. In the case of stage IIl, partial resection of invaded surrounding organs is added. We often perform preoperative corticosteroid therapy to shrink the tumor. In the case of stage IV a with pleural dissemination, thymothymomectomy with resection of all dissemination lesions is performed. The case with widespread invasion to pericardium and pericardial dissemination are considered as inoperable and undergo chemoradiotherapy. Postoperatively radiotherapy is added in the case of stage III and IV. In elderly patients 5 and 10 year survival rates were 60.2 and 48.1%. These were significantly worse compared to young patients. It depended on postoperative complications as sternomyelitis and different kinds of critical complications.