ARTICLES 727 However, these differences were not statistically significant. The retardation of skeletal maturation of subjects No. 3 and 5, the 2 boys exposed at 16 to 17 months of age, is even more extreme than the retardation in their statural growth. Their skeletal maturation has fallen progressively farther behind the standards of Greulich and Pyle each year, and they are now approximately 6 years retarded according to these norms. One of these boys (No. 3) is shown with his younger (larger) sib (No: 83) in Figure 7. The roentgenograms of the wrist (Fig. 8) as well as the graphic presentation of the osseous development (Fig. 9) indicate the magnitude of retardationin this particular tga boy. The exposed girls did not differ significantly from the unexposed girls with respect to skeletal maturation, but it is perhaps of interest to note that the girl who has consistently been the most retarded in -skeletal maturation (27 months below Greulich and Pyle standards), and the smallest for age of the exposed girls, was exposed at 15 months of age. This would be consistent with the viewpoint that chil- dren are most susceptible to the effects of exposure in the l-year-old age range, but ey Be that girls are less susceptible than boys. There were nosignificant differences between the children born to exposed parents and the children born to unexposed parents with respect to stature, weight, head cir- cumference, or skeletal maturation. Although the exposed category consisted of 31 children who had received 175 r and 7 who had received 69 r, there was no difference in the growth patterns of the children receiving the two different doses of irradiation. Therefore, the two groups were combined in the analytic procedures. COMMENTS Among the most prominent findings of the present study has been the age and sex dependence of the effects on growth of the Marshallese children. Boys appeared to be more adversely affected than the girls; the Fic. 1 Brothers. Marked retardation 3in statural growth is shown by the older (shorter) brother (No. 3 on the right) who was exposed at age 4 months. The younger, by 21 months (No. 83 on the left), is taller by 13 cm. The retarded boy showed no evidence of hypothyroidism or skeletal disease clinically other than markedly delayed osseous maturation. 6~ Sep retardation was noted among boys exposed at ages below 5 years. Those who were 12 to 18 months old at the time of exposure to fallout radiation have shown the greatest deviations in growth patterns. From a preliminary survey in 1947 and 1948 of children who were exposed to the atomic bomb in Nagasaki and Hiroshima, Japan, Greulich e¢ al.?4 reported that the growth and development of the surviving children were retarded. They also found that the boys tended to be moreaffected than the girls. This sex-connected inferiority in adjustingto stress situations had been noted in earlier studies on Guamanianchildren by Greulich.”” In a broad program of medical observa- tions, the Atomic Bomb Casualty Commis- sion (ABCC) has continued to study the ey