We retrospectively reviewed our series of 390 consecutive patients operated on for Graves' disease from 1983 through 2002 at Tenri Hospital. Of the 390 patients, twelve (Group A) were found to have thyroid carcinoma, eleven papillary and one follicular, for an incidence of 3.1%. In 58% of these cases the tumors were less than 1 cm in diameter and only one patient had recurrence in the cervical lymph nodes. All patients are alive without disease. There was no correlation between the TSH-binding inhibitory immunoglobulin titer and the progression of their carcinomas. Ninety-seven (Group B) patients who had been surgically treated for differentiated thyroid carcinoma from 1999 through 2002 were selected for comparison. The mean age at operation in Group A was 38. 8 years, younger than that of Group B, 55.2 years. However, there was no difference in tumor size, and intrathyroidal, lymphatic and distant metastasis between the two groups. Our results suggest that Graves' disease is not associated with increased or rapid growth of concurrent thyroid carcinoma.