281 CONARD ET AL. During the past survey the differential counts showed eosinophilia above 35% in about half of the people of both groups. 6. Hematocrit Erythropoietic activity as evidenced by hematocrit readings has not shown any remarkable change since exposure. The values have been consistently on the low side of normal, according to American standards, particularly in the females in both exposed and unexposed people. The hematocrit readings after + years were about the same as found at 3 years and about equal to the comparison populationlevel. B. Prysican Finpincs 1. Diseases There have been no diseases, infectious or noninfectious, that could be related to irradiation effects. No antibiotics, blood transfusions, or other specific therapy has been used either prophylactically or therapeutically in the Marshallese, even during the acute period when maximum depression of the blood elements was noted. The incidence of diseases in both the exposed and comparison populations has been about the same. Even when leukocyte depression was greatest (the levels reaching about half of the levels of the comparison population at about 5 to 6 weeks postexposure) there was apparently no increased susceptibility to infection. An epidemic of upper respiratory infection that occurred at this time showed no greater incidence or severity in the exposed people compared to the unexposed. There was no bleeding associated with a maximum depression of platelets (11 individuals had platelet counts between 35,000 and 65,000). The people have since sustained epidemics of measles, chicken pox, upper respiratory infections, and gastroenteritis without untoward reactions. A limited study of the immune response at 3 years postexposure showed that the antibody response to tetanus toxoid antigenic stimulus was not significantly different in the exposed and unexposed people at that time. During the past year 5 exposed children and 1 unexposed child presumably had infectious hepatitis. No other serious illnesses were reported. Three deaths have occurred in the exposed people. Thefirst. was in a 46-year-old man who died of hypertensive heart disease 1 year postexposure. He had had the disease at the time of irradiation. The second death occurred in a 78-year-old man at 2 years postexposure. He was a diabetic of long standing and died apparently of coronary heart disease. A third death occurred in April, 1958, in a 38-year-old mun. (He was in the group that received 69 r.) Death was due to pneumonia complicating a severe case of chicken pox. In none of these cases was there any evidence that death was due to irradiation exposure. 2. Growth and Development Studies Data on height and weight and bone age determinations for the 2- and 3-year surveys gave an impression of lag in growth and development in the exposed