where 144 people were examined. The ship served as a base of operations and laboratory (Figure 2). The physical examinations at Utirik were carried out in tents ashore (Figure 3). Several unfavorable factors associated with the examinations should be mentioned: 1) The language barrier made the examinations difficult since very little English is spoken by the Marshallese. However, sufficient interpreters have been available to assist the medical team. 2) The lack of vital statistics from the Marshallese imposes a serious difficulty in interpretation and evaluation of the medical data. Such statistics would be extremely helpful in evaluating the long-term effects of radiation. In recent years records of births, deaths, etc., have been kept by the health aids or magistrates and supposedly forwarded to the district administrator; however, such records have been poorly kept or lost and thusvital statistics are practically nonexistent. 3) Another factor was the uncertainty ofexact ages of some of the Marshallese, particularly in the older groups, largely due to lack of written birth records. Exceptfor thefirst, birthdaysarelittle observed. 4) The medical status is also complicated by unhygienic living conditions evidenced by the presence of parasitic infestation, chronic skin diseases, and extremely poor oral hygiene. Possibly dietary de- ficiencies also exist (this will be further evaluated on later surveys). 5) During the course of these studies over the past three years, difficulties have been encountered in obtaining what could be considered as entirely adequate populations to act as comparison groups for the irradiated people. Two separate comparison groups had been used in the past, each comparable to the exposed group in size and closely matchedfor age andsex. These groups are represented in hematological graphsof this report as A and B (B, and B,). The A population was chosen at Majuroat the time of the initial examinations, but at six monthspostexposure it was found necessary to select another group, the B, group, since many membersofthe A group were missing (had migratedto otherislands, etc.). At the two-year examination, the B group (8, ) was used again even though about one-third of the group was missing. The people in the A and B groups were mostly Marshallese from the eastern chain of the Marshall Islands and are considered to be anthropologically slightly different from people of the western island chain to which the Rongelapese understudy belong.® At the time of the present survey, it was found that during the preceding year the Rongelap population had doubled at Majuro Atoll by the influx of other Rongelap people who had been away from theisland at the time of the accident but had since returned. This situation was most fortunate, since this group of people was of the same stock (blood relatives) and wasliving with the population under study underthe same environmental conditions. These people provided a uniquely appropriate group to serve as a comparison population. Moreover, they matched reasonably well for age and sex and would beavailable for future examinations since they planned to return to Rongelap Island to live. This group is represented as Cin the graphs. For the growth and development studies, as many of the old B-group children as could be found were examinedin addition to the Rongelap children in order to expand the number for comparison and furnish further longitudinal data for yearly studies. EXAMINATIONS Histories were taken by a Marshallese practitioner with particular emphasis on the interval history during the past year. Complete physical examinations were carried out including examination of the skin with color photography andbiopsies of selected lesions; ophthalmological studies includingslit-lamp observations, visual acuity, and accommodation; growth and developmentstudies in children (less than 20 years of age) including anthropometric measurements and x-ray examinationsofthe left wrist and hand for bone developmentstudies; audiometer examinationsonall over 30 years of age; ECG records on all over 40 years of age; and x-ray examinations as deemed necessary. Hematological examinations included three complete blood analyses including WBC,differential, platelet counts (phase microscopy), and hematocrit (microhematocrit method) done at about weekly intervals. (Only one complete blood study wascarried out on the Utirik people except for repeat examinations on those with abnormal counts.) In addition, sickling tests (sodium bisulfide technique) were run, and smears were obtained for reticulocyte counts, alkaline phos-