Purpose : Graves' disease is the most common cause of hyperthyroidism in children and adolescents. In this study, we investigated the natural course and the prognostic factors of Graves' disease in Korean children and adolescents. Methods : One-hundred thirteen (88 girls and 25 boys) patients were included in this study. A retrospective analysis was made of all patients who were diagnosed with Graves' disease. The following parameters were recorded and analyzed: patient's sex, age at diagnosis, duration of disease, laboratory findings, symptoms and signs, and family history of autoimmune thyroid disease. Results : All patients were initially treated with antithyroid drugs, either methimazole (93.8%) or propylthiouracil (6.2%). Antithyroid drugs had been discontinued in 75 (66.4%) of 113 patients. Of these 75 patients, 23 (20.4%) relapsed after 25.5¡?#?3.7; months. Thirteen (11.5%) of 23 patients, who experienced the first relapse, showed a second remission. However, 2 (1.8%) of 13 patients relapsed again. Euthyroid state could not be achieved by antithyroid drugs in 1 patient, and radioactive iodine therapy was performed. The older the patient at diagnosis, the greater the likelihood of remission (P =0.034). Conclusion : Age at diagnosis seems to be a prognostic factor in Korean children and adolescents with Graves' disease, and should be taken into account in treatment plan determination.