Abstract
Thyroid dysfunction in patients with Down's syndrome is well known. Although the majority of children with Down's syndrome appear to have normal thyroid function, however, hypothyroidism is commonly seen. The presence of hyperthyroidism is rare. The etiology is believed to be autoimmune. We report a patient with Down syndrome and Graves' disease who responded well to antithyroid drugs. The rarity of this association, especially in a child younger than eight years of age, has prompted us to report this case.