We report herein rare cases who developed hyperthyroid Graves' disease after surgical treatments for thyroid nodules. We have seen only 4 such cases in the course of 1680 consecutive cases (0.24%) of thyroidectomies in which partial thyroidectomy was carried out from 1966 to 1993. It is of interest that because 2 of these three cases (67%) were associated with positive TGHA and/or MCHA at the time of surgery, the presence of autoimmune thyroiditis may predispose to Graves' disease, but surgical treatment of the thyroid glands may not be related to the development of Graves' disease, because the hyperthyroid symptoms appeared 2 to 27 years (mean: 12 years) after the surgery.