During the last year, we have been impressed by a great increase in the incidence of hyperthyroidism and particularly by the appearance of an unusual type of thyroid hyperactivity in men. We have therefore made a special study of these cases with particular reference to the possible etiologic factors involved, and have found that the accumulated evidence seems to point conclusively to the continued ingestion of small amounts of iodine in the insidious form of iodized salt as the primary exciting factor. For this reason, we feel that it is important to call the attention of physicians, and through them of the public, to the misunderstanding that has gradually arisen regarding the use of iodine in endemic goiter, particularly in the form of iodized salt. Without any precaution being given for its use, this salt is being vigorously promoted by the combined propaganda of health officials and of salt companies,