Radiation-Associated Thyroid Carcinoma 253 the present data the risk of developing radiation-induced thyroid neoplasia is probably underestimated, since surgical removal of potentially malignant tissues may have occurred and the hormone treatment may have inhibited the development of some tumors. Also, as Qo ae! pointed out above, the true carcinogenic potential of the exposure, particularly in the children receiving the higher dose, may have been masked by excessive cell destruction. The recent finding that subclinical thyroid deficiency is present in some of the exposed people who have not shown any thyroid abnormalities also indicates that the thyroid effects in the Marshallese may not yet be completely manifest, and continued careful surveillance of this population is necessary. a o> Q MARSHALL [ISLANDS a QO Fig. 1. 1, 1954. = ° MAJUAO S b Map of fallout area, Marshall Islands, March