Surgery is considered standard therapy for nontoxic goiter. However, surgical treatment of large goiters is not without risk, especially in elderly patients and in those with cardiopulmonary diseases. Therefore, in recent years interest in 131I treatment of nontoxic goiter has increased. Studies, using ultrasonography and magnetic resonance imaging (MRI) for accurate measurements of thyroid volume, have shown that 131I treatment of nontoxic nodular goiter results in a mean thyroid volume reduction of 40% after 1 year of 50-60% after 3-5 years. Moreover, an improvement of compressive symptoms can be achieved. This has been objectified by a significant decrease in tracheal compression as measured by MRI. Early side effects due to radiation thyroiditis usually are mild. The development of autoimmune hyperthyroidism occurring several months after 131I therapy in approximately 5% of patients is the most important complication of 131I therapy for nontoxic goiter. The incidence of post-treatment hypothyroidism appears to be approximately 20-30% at 5 years. For elderly people, the lifetime risk of fatal and nonfatal cancer induced by this therapy (administered activity 1.9 +/- 0.9 GBq of 131I) was estimated to be approximately 0.5%. In all patients with nontoxic multinodular goiter the estimated risks of both surgery and radioiodine therapy should be weighed carefully. In younger patients surgery still is to be preferred, especially when the amount of 131I to be administered is high. However, for elderly patients, especially those with cardiopulmonary disease, the profits of radioiodine treatment will outweigh the lifetime risk of this mode of therapy.