One hundred sixty-six patients underwent operation for myasthenia gravis between 1977 and 1989. Thirty-eight patients had associated thymoma, registering stages I (n = 17), II (n = 9), III (n = 11), and IVa (n = 1) according to the classification of Masaoka and colleagues. Extended thymectomy was performed on 128 patients without thymoma; thymothymectomy, with resection of the anterior mediastinal fat and tissues adherent to the tumor, was performed in all patients with thymoma. There were no instances of early or late death. Neuromuscular function improved, and clinical myasthenic symptoms stabilized in almost all patients except 2 patients in stage III and 1 patient in stage IVa, who had an exacerbation of the myasthenic symptoms associated with recurrence of thymoma. All the recurrent tumors were on the pleura and could be resected. The suspected cause of recurrence is either dissemination of tumor cells as a result of operative manipulation or undetected disseminated foci that existed at the time of the first operation. The resections of the recurrent invasive thymomas localized on the pleura were easily performed and improved the myasthenic symptoms.