volume.Eleven patients developed hypothyroidism (cumulative five year risk 22%, 95% confidence interval 4-8% to 3844%). Side effects were few: three cases of hyperthyroidism and two cases of radiation thyroiditis. Only one patient was dissatisfied with the result; she was referred for operation six months after treatment. Conclusions-A substantial reduction in thyroid volume accompanied by a low incidence of hypothyroidism and few side effects makes the use of radioactive iodine an attractive alternative to surgery in selected cases of nontoxic multinodular goiter.