Background: Hyperthyroidism (HT) prevalence is 0.1/100,000 children and 1/100,000 adolescents and Graves Disease is the most frequent etiology. Objective: To evaluate the clinical presentation, etiology and treatment in hyperthyroid children. Method: Retrospective review of clinical charts of children under 15 years-old, between June 2004 and August 2005. Hyperthyroidism diagnosis was performed with suppressed TSH and increased thyroid hormones levels. Etiological study was done by TRAb, ATPO, ATG, thyroid echotomography and I 131 capture. Results: 26 patients were evaluated; 84.6% females and age at diagnosis was 9.8 ± 3,5 years-old (range: 3,8 - 14,5). Goiter was the most frequent clinical sign (96,2%), tachicardy and swelling. Etiology: Graves Disease (73%), Hashitoxicosis (15,3%) and unknown etiology (11,5%). Treatment: 88,4% began with anti-thyroid drugs (DAT): 78% PTU and 22% Tiamazol. 62.5% became euthyroid after 6 months and 79.1% after 12 months. 31.5% of GD presented hypothyroidism at 6.3 ± 4 months of DAT, requiring LT4 substitution. I 131 was applied to 4 children (16.6%); 3 due to hepatic compromise pre or post PTU use and 1 girl for missing treatment, developing a thyrotoxic torment. Thyroidectomy was done in 2 patients (8.3%), both with GD; 1 for giant goiter without DAT response at 19 months and 1 for persistant hyperthyroidism after 25 months of DAT. 92% received β-blockers (Propanolol) for adrenergic symptoms for 5 ± 4 months. Conclusions: Goiter was the most frequent pediatric HT symptom and Graves disease the main etiology. DAT treatment control HT in 76.9% patients and no adverse reactions with I 131 were observed. These results promote DAT treatment as first line in HT management, prefering Tiamazol for its better adherence and less adverse reactions. Radioiodide therapy and thyroidectomy are alternatives if treatment fails in pediatrics HT.