Each of the three major therapies for Graves' disease has its own advantages, disadvantages, indications, and contraindications. Today, radioactive iodine (RAI) therapy is the most commonly used therapy for Graves' disease in the United States, with approximately 70% of patients so treated after initial presentation and an additional fraction of arguably 10% to 15% treated with RAI after failure of antithyroid drugs or surgery RAI therapy is acknowledged to have the clear-cut advantages of safety and very low morbidity and cost. For most patients with Graves' disease, the indications for RAI therapy are clear and noncontroversial. Moreover, RAI treatment is now being considered by some thyroidologists for “subclinical” thyrotoxicosis (normal T4/T3 but immeasurable thyroid-stimulating hormone), particularly in patients more than 45 years of age. because of concerns of the risks of atrial fibrillation, although some favor a more conservative approach to this group of patients. RAI therapy is not considered indicated, or is frankly contraindicated, in pregnancy; nursing women; and patients with subacute thyroiditis, postpartum thyroiditis, struma ovarn, pituitary (thyroid-stimulating hormone-driven) hyperthyroidism, euthyroid hyperthyroxmemia, or thyroid hormone resistance. Opinions on the use of RAI therapy in children vary in terms of the youngest patient with Graves' disease who would be treated; generally, a lower age cutoff of 1 7 years is acceptable in most clinics. Even more controversial is whether RAI therapy in the presence of Graves' ophthalmopathy constitutes a risk for worsening ophthalmopathy. Resolution of this latter issue awaits more definitive studies, but RAI therapy is likely to remain the first choice for most patients with Graves' disease.