Patients and methods. - The initial symptomatology and long-term effects of antithyroid drug treatment are reported in children aged 11.7 +/- 3.2 years (52 girls,16 boys) with hyperthyroidism due to Graves' disease. Results, - A family history of thyroid pathology was found in half of the cases: 7% (five out of 68) of our patients have had another autoimmune disorder associated with hyperthyroidism. The most frequent and permanent clinical symptoms at diagnosis were goiter and tachycardia. Antithyroid drug treatment was always proposed at first line and resulted in a rapid decrease in clinical and biological signs of hyperthyroidism. Subtotal thyroidectomy (n = 19) was mostly performed because of non-compliance or recurrence of hyperthyroidism after medical treatment withdrawal. Significant adverse reaction (leukoneutropenia) was observed in only one patient. Survival remission times analysis (remission being defined as clinical and biological euthyroidism for more than I year after antithyroid drug withdrawal) realised in 50 subjects followed up for at least 2.5 years showed complete remission in 55% of the patients treated exclusively medically (n = 27), when lost to follow-up or surgically treated subjects were considered as incomplete observations. On the whole studied population (n = 50), the remission rate was of 30% (n = 15) with an average follow-up period after medical therapy withdrawal of 5.2 +/- 3.0 years (range: 1.4-12.3 years). At present, ten out of 15 can be considered as healed (remission time for at least 2.5 years). Moreover, according to survival analysis, 75% of the remissions have a probability to occur in a delay of 4.6 +/- 1.0 years after the beginning of medical treatment. Conclusion. - In this population, no remission after 7 years of antithyroid drug therapy was observed. Remission predictive factors remain to be defined. (C) 1998, Elsevier, Paris.