Apart from MG with a thymoma, the finding of the titin autoantibodies was observed to be an exclusive feature of late-onset MG, the frequency being 55%. No data were found to suggest that patients with MG were more likely to present with thymic tumors than other patients exhibiting thymic neoplasia. In about 80%, such tumors in MG were composed of cortical cells. The concept of the anti-titin antibodies merely as a paraneoplastic marker in MG was not supported by these data.