SUMMARY Among the 67 people of Rongelap island now living (of the original 82) who were accidentally exposed to radi active fallout in 1954, 3 have developed a malignant lesion of the thyroid, 16 have developed benign nodules of the thyroid and 2 have atrophy of the gland with hypothyroidism. These findings - indicate the seriousness of the exposure to radioiodines in fallout. The . preponderance of thyroid lesions have occurred in persons who were children less than 10 years of age when exposed. Thyroidectomy, partial to complete, has been carried out inthe United States on 18 Marshallese persons. " €indings are described, The Slight retardation of growth in some of the exposed - _children is correlated with demonstrable deficiency of the thyroid hormone | associated with radiation-induced lesions of that gland. ' Supplemental | | thyroid hormone treatment seems to be promoting skeletal growth in some’ _ . _ of these children. The possible influence of puberty and pregnancy in the development of the thyroid lesions is pointed out. The calculated risk of a malignant lesion of the thyroid in the Marshallese varied between 3 and 10 cases per 10° persons per rad per year for the different age groups. Based on these few cases the riskfor thyroid cancer from radioiodine exposure does not appear to be very different from that reported in persons following X-radiation of the neck region as children, DOE ARCHIVES . JK