~24- woman with a cancer of the gland. The development of marked thyroid deficiency in 2 boys who showed greatest growth retardation and to a lesser degree in several other children clearly indicates the correlation of thyroid deficiency with growth retardation in the exposed children and emphasizes the seriousness of such thyroid exposure in children. Though dose estimates for the thyroid glands are only approximate, the Marshallese experience helps to define the dose range in which thyroid damage may occur. Preliminary evaluation of the effects of thyroid hormone therapy in the Marshallese indicates that such therapy may be of value, both as a prophylatic measure to prevent development of thyroid abnormalities including malignancy and for therapeutic reasons to restore growth and development in children with injured thyroid glands. It can be concluded that though the acute effects of exposure to large amounts of radionuclides taken internally may be negligible the possibility of serious late effects of injury to the thyroid gland is of considerable importance. There has been no indication in the Marshallese that the bone seekers such as 29Sr or other radionuclides absorbed have produced any significant effects.