It is generally assumed that adult height is attained when the skeletal age is 17 to 13 years in girls and 18 to 19 in boys (50,52,248), but actual measurements on the Marshaliese population showed that many subjects cont inuez to increase in stature with advancing chronological age, even after age 3G, 2.- though the late increments were almost always very small. After the Marshallese reached age 16, absences from the island at the time of survew became more frequent; therefore, the time when adult stature was actually attained is uncertain for manv individuals. Statistical analyses ‘Appendix III} of the data on adult (fimal) stature of the Rongelap inhabitants who were in the pediatric age group on Marsh [, 1954, gave the following results: * In the unexposed grous, Zor both boys and girls, * In the exposed group, for both boys and girls, there was no signit- cant difference in mean adult stature between those born after 1944 (<10 wears old on March 1, 1954) and those born before 1945 (>10 years old on March L, 1954). there was ao signrfi- caat difference in mean adult stature between those born after 1944 and those born before 1945. * For both boys and girls, there was no significant differeace in mean adult stature between those who were exposed on Rongelap and Ailingnae to fal— out radiation and those who were not. Since osseous maturation is dependent on normal thyroid funetion, it is reasonable to assume that its retardation in exposed children was dwe to radiztion damage to the thyroid glands. The marked retardation of skeletal natmration tollowed by dramatic improvement after the administration of thyroid mor— mone has been documented in the children who were clinically hypothyroid (13). The catch-up phenomenon in respect to osseous maturation can reasonably be attributed to the administration of thyroid hormone to the exposed populations, many of whom were subclinically hypothyroid (see Section IX.C.2). - 31 +