nam 3 phocytes were considerably depressed and thatsignificant doses of radiation had probablybeen re- ceived. In addition to the whole-body dose of radi- ation andthe betairradiation of the skin, radiochemical analyses of the urine showed that measurable amountsof radioactive material had also been absorbed internally. The effects of the radia- tion can best be summarized underthree headings according to the modeof exposure: penetratingirradiation, skin irradiation, and internalirradiation. PENETRATING RADIATION Oneofthe earliest findings indicative ofa significant exposure in these people was lowering of levels of leukocytestimd platelee@ef the peripheral blood. This was most marked in the 64 people on Rongelap who had received £75gads, and was less marked in the other groupsrnreceiving less exposure. The hemajgoicticdeprétsion-was roughly pro- portionate thédose of radiation.received., Even in the 157 Utirik’peopligavtio received only an esti- mated 14,rads, it was possible.to distinguish slight platelet depression inthe group as a whole. The smaller growp on Ailingaac and Rongerik showed peripherak blood levels between those ofthe-high-- and low exposure groups. The chronological recordsof blood findings on the group exposed on Rongelapare presented in Figures 49, 50, 56, and 65 and Appendix 8, and on the Ailingnae and Utirik groups in Appendices 9 and 10. Lymphopenia of about half the level of the comparison Marshallese population was evident when the peopie exposed on Rongelap-werefirst examined on their arrival at Kwajalein 3 days after exposure (see Figures 49, 50, and 65). In children <5 years of age the lymphocytes dropped to 25% of the levels in the comparison children, but showeda slight rise during the following weeks. The lymphocyte level showed a slight increase by 1 year. In the following year mean counts approachedthe levels of the comparison population but remainedslightly below (see Figures 50 and 65). Neutrophil levels fluctuated considerably during the first month; possibly this was related to the prevalence of beta burns of the skin during that period. Neutrophil depression becameevident by 5 and 6 weeks post exposure (see Figures 49 and 65), with levels reaching about half that of the comparison population in the adults and slightly lowerin the children <5 years of age. This degree of neutropenia wasinsufficientto result in any apparentincreased infectious.processes, and, indeed, it was noted that neutrophilic leukocytosis was possible in people showing casualinfectionsat this time. Neutrophil levels recovered more rapidly than lymphocyte levels and reached near control levels by | year. Subs@quent annual surveys have revealed that recovery does not appear to have been complete, particularly in younger and older age groups, during the 10-year period. Early platelet counts showedless fluctuation than other blood counts and fairly consistently showed increasing depression, reaching levels of about 30% that of the comparison population by the 4th week. A spurt of recovery to about 75% of comparison levels occurred during the following few weeks,awhich was followed by slower recovery but.with meanlevels nevér reaching higher than 90 #6 95% that of the compagjson population dur- ing the 30 years post expordy(see,Figures 56 and 65). ™ Erythropoietic depression has not been a consistent finding as with the leukocytes and thrombo- cytes. Slight depression of red blood counts, hematocrits, and hemoglobin has been noted at times. Bone marrow smears taken at 6 months showed no gross abnormalities. Smears taken at8, 9, and 10 years showed an alteration in the mveloid-erythroid ratio manifested by an increased numberofred cell precursors. Depression of peripheral blood elements in the Ailingnae and Rongerik groups was not so pronounced asin the Rongelap group. However, a slight lag in complete recovery in the Ailingnae peripheral blood count has also been noted. Thepersistent depres- sion of peripheral blood elements in the exposed people makesit appearlikely that there is slight residual bone marrow damage. A general anemic tendency has been evident in both exposed and unexposed Marshallese. PriceJones curves, on the average, showed slight microcytic tendency. Serum iron levels have been generally normal, and the cause of this anemic tendency has been undetermined. Reticulocyte counts have been about the samein the exposed as in the unexposed peopie. Clinical findings, except for radiation-induced lesions of the skin, patchy epilation, and early gastrointestinal symptoms, revealed no clear-cut disease processes or symptomswhich could bere-