Radioiodine treatment of benign thyroid disease has a 60 year history. Among the radioactive isotopes (131)-I can be used successfully. This method has been spread at different rate over the world. Radioiodine is used in Hungary since 1959, however, incidence of this type of therapy does not reach an optimal proportion. The aim of therapy is to decrease the function and/or the volume of thyroid gland. This study considers the reasons of radioiodine treatment in Graves' disease and in different forms of autonomously functioning nodular thyroid disorders, moreover, in cases of compressive euthyroid multinodular goiter when the thyroid volume is to be diminished. There are controversies in terms of indications of radioiodine treatment, however, contraindications are generally well accepted. Sometimes radioiodine therapy could exert an unfavourable effect on ophthalmopathy but this can be prevented with steroids. In cases of suitable administration of thyrostatic treatment before (131)-I therapy the outcome of which does not change significantly though propylthiouracil has really some radioprotection effect. Excellent cure rate can be reached in Graves' disease with radioiodine but hypothyroidism after the treatment may be frequent. In cases of autonomously functioning nodular thyroid disorders (i.e., toxic uninodular or multinodular goiter) cure rate is as high as in Graves' disease but the incidence of thyroid hypofunction is much lower. Thyrotoxic crisis after the treatment is extremely rare. In some cases thyroiditis can be observed after (131)-I therapy but this condition can be easily managed. Thyroid radioiodine uptake and the effectiveness of (131)-I can be increased with the administration of recombinant human thyrotropin in cases of euthyroid multinodular goiter. Recently radioiodine is recommended to young patients having Graves' disease (over 15 years) in special cases. The risk of malignancy after isotope therapy is not significant. Radioiodine treatment of benign thyroid disorders is a simple, safe and cost-effective method, the propagation of which can be suggested.