Graves' disease is a common condition encountered in clinical practice. The available modes of therapy for Graves' disease are antithyroid drugs, radioiodine and surgery. Radioiodine therapy is indicated in patients with nearly all causes of hyperthyroidism and is considered the treatment of choice for most patients with Graves' hyperthyroidism who are beyond the adolescent years. Pregnancy and breast-feeding are absolute contraindications. Although there are many ways of calculating the dose of radioiodine, fixed dose regimens are gaining acceptance. Hypothyroidism follows sooner or later in nearly all patients treated with radioiodine. Available evidence suggest that patients are best treated by a single thyroablative dose, the aim being elimination of hyperthyroidism, with larger doses accomplishing it with more certainty, and the inevitable hypothyroidism develops under physician control. Radioiodine therapy can lead to exacerbation of infiltrative ophthalmopathy and this can be prevented by the concomitant administration of corticosteroids. Radioiodine therapy for Graves' hyperthyroidism has no adverse effects on the health of the offspring of treated patients. There are no definitive data that provide evidence for increased rates of thyroid cancer, leukaemia, infertility or neonatal abnormality in patients treated with radioiodine. Radioiodine therapy is safe, definitive and cost-effective.