Observations The latest findings are based on the annual medical survey carried out at Rongelap in March 1959 at five years after exposure. About 100 exposed people including their children and 200 unexposed people were examined. ‘Since the data are not yet completely analyzed, the statements made con- cerning this survey must be considered as preliminary in nature. The survey was conducted by a 20 man medical team from various institutions in the United States under the direction of Brookhaven National Laboratory. The examinations included medical histories, complete physical examinations, and blood and other laboratory examinations. In addition body burdens are being determined from spectrographs of gammarayactivity of 175 Rongelap individuals and from numerous radiochemical analyses of urine samples. Acute effects of gamma irradiation During the first 24 to +8 hours after exposure about 2/3 of the Rongelap people experienced anorexia, nausea, and a few vomited and had diarrhea. Many also experienced itching and burning of the skin and a few complained of lachrymation and burning of the eyes. Following this they remained asymptomatic until about two weeks after the accident when cutaneous lesions and loss of hair developed due largely to beta radiation of the skin. It was apparent when the people were first examined, a few days after exposure, that the lymphocytes were considerably depressed and that significant doses of radiation had probably been received. The dose of radiation proved to be sublethal since no deaths occurred which could be directly related to radiation exposure. However, it is probable that the dose was in the high sublethal range judging by the degree of hemopoietic depression that developed. In addition radiochemical analyses of the urine also showed that definite amounts of radioactive material had also been absorbed internally. The changes during the past five years in the mean peripheral blood levels of the more heavily exposed group of 64 Rongelap people receiving approxi- mately 175 r of whole-body radiation are shown in Figures 2, 3 and 4. The white blood cell levels of the exposed group were depressed to about half those of the unexposed comparison population during the first two months but no related untoward effects were observed in these people. No increased incidence of infection was observed and no therapy (antibiotic or otherwise) was given specifically for their leukopenia. Mean blood platelet levels were also significantly depressed to about 30 per cent of the unexposed levels by the fourth oo mS Pao oa? or 316