Two cases of Graves' disease emerging in previously hypothyroid patients are described. After two years of thyroid hormone substitution due to 'idiopathic' hypothyreosis (patient 1) and Hashimoto's thyroiditis (patient 2), the substitution had to be stopped. The persisting clinical and laboratory signs of immune hyperthyreosis, including positivity for TBII and TSAb, were accompanied by the signs of mild ophthalmopathy. The antibody-spectrum changes during the course of the disease are discussed.