This report describes two unusual cases of subacute thyroiditis from which Graves' disease with hyperthyroidism developed seven to eight years after complete recovery. The first case is a 45-year-old woman who developed hyperthyroidism seven years after recovering from subacute thyroiditis. This patient had a genetic predisposition to both subacute thyroiditis HLA-BW35 and Graves' disease (HLA-BW46). The second case is a 60-year-old woman who developed hyperthyroidism eight years after the episode of subacute thyroiditis; her HLA showed neither BW 35 nor BW 46. It has been reported that if hyperthyroidism is to develop following subacute thyroiditis it occurs within one year. Our observation indicates that it may occur seven or eight years later.