THE THYROID gland has the ability to concentrate the isotopes of iodine, and this selective uptake is increased greatly in hyperplastic disease of the thyroid gland. Since the initial investigations by Hertz, Roberts and Evans,1Hamilton and Soley2and Hertz and others3there have been numerous reports on the use of radioactive iodine (I130and I131) in the treatment of patients with hyperthyroidism. The various investigators differ somewhat concerning dosage and the management of their patients, but the basic approach is the same. An initial calculated dose of radioactive iodine is administered orally to the patient, and the majority of investigators prescribe additional therapy as indicated by the subsequent course. Since we studied over 200 patients in the two and a half years previous to this report, we believe it worth while to record our experience. MATERIAL The data were sufficiently complete to justify conclusions