The authors report two patients presenting myasthenia gravis, respectively, 4 years and 2 months, and 6 years and 7 months after total resection of thymoma. Computed tomographic scan and magnetic resonance imaging did not show any signs of recurrent or metastatic thymoma. Pyridostigmine bromide was successfully administered in both patients. The late onset of autoimmune disorders should be kept in mind as possible and, sometimes, fatal complications of surgical treatment for thymoma. In all cases, recurrent or metastatic thymoma should be ruled out because reoperation may be effective even in the treatment of myasthenia gravis.