7 higher than after six months. Hematocrit determinations first done on the 22nd day wereslightly below those of the control population. A significant trend in values after this time could not be detected statistically. The lessexposed island groups showed similar, but in most cases less pronounced, hematological change that was consistent with the lower doses calculated for these groups. The time course of hematological changes corresponded most closely with the low-dose Japanese groups exposed to radiation from the Hiroshima and Nagasaki bombs* in which definite signs of severe radiation exposure were present in some individuals but in which no mortality occurred. Comparison with hematological data in Japanese groups in which fatalities occurred make it probable that exposure in the highest exposure group of Marshallese was moderately severe, probably within 50 to 100 r of the level where somefatalities would have resulted. The skin and internal radioactive contamination were considered not to have contributed significantly to the depression of the hematological elements. The body weight of individuals in the Rongelap and Ailinginae groups was followed routinely. Adults as well as children lost some weight during the period of observation in spite of the fact that they lived inactive lives and ate heartily. Whether the failure to gain weight was connected with radiation or change in environmentis open to question. Four women in the Rongelap group were pregnant when brought to Kwajalein. None of these women had abnormal symptomsreferable to radiation. All of the pregnancies have since terminated in delivery of apparently normal babies. SKIN LESIONS AND EPILATION Irradiation of the skin resulted largely from beta radiation from the fall-out material deposited on the skin. Due to the complex composition of the radioactive ma- terials, and because of other uncertainties, it was impos- 3. LeRoy, G. V.: Hematology of Atomic Bomb Casualties, Arch, Int. Med. 86:691 (Nov.) 1950. Oughterson, A. W., and others: Medical Effects of the Atomic Bombs, report of the Joint Commission for Investigation of the Effects of the Atomic Bomb in Japan, vol. 3 and 5, Office of Air Surgeons, Army Institute of Pathology, Atomic Energy Commission, 1951.