Introduction This report updates, for 1980 through 1982, the results of continuing medicalsurveillance of a Marshallese population accidentally exposed to radioactive fallout in March 1954. It is the sixty-fifth in a series of publications from the Medical Department, Brookhaven National Laboratory, concerning the effects of that exposure, all publications being listed in the Reference section beginning on page 16. Manyof these publications include details of the acute effects suffered by the Marshallese and the radiologic assessments at the timeof, and sub- sequent to, the fallout, with the most recent summary being Dr. Robert Conard’s 26-year review.A recounting of those events is therefore not included in this report. The originally exposed Marshallese population comprised 64 persons on Rongelap Atoll whoeachreceived, on the average, an estimated 190 rads of absorbed external gamma radiation, 18 on Ailingnae Atoll who received 110 rads, and 159 on Utirik who received 11 rads (see AppendixI for the derivation of these new dose estimates). There were, in addition,3 persons in utero on Rongelap, 1 person im utero on Ailingnae, and 8* persons in utero on Utirik who are considered exposed. Under the Brookhaven National Laboratory program, the recipients of primary medical care include exposed and comparison populations as well as a rather large numberof additional beneficiaries who are seen on a humanitarian basis of practical need and resource availability. In recent years, about 1400 people have been seen annually. This report, however, deals with four clearly defined groups: the remaining individuals who were exposed to radioactive fallout on Rongelap, Ailingnae, and Utirik in 1954 (including those in utero), and a comparison population of individuals from Rongelap who were unexposed. The number of persons now in each exposure category are 51, 12, 116, and 137, respectively. The unexposed comparison group, which was individually matched by age and sex against the combined Rongelap and Ailingnae groups in 1957,” has varied in composition over the years as some individuals have voluntarily withdrawnor been lost to followup and others csi Co aD C4 Cc cn *This number includes two previously unidentified persons confirmedin 1982 as being exposed in utero. have been added. There has been, in addition, the expected natural mortality. Despite these factors, chi-square values based on contingency table analysis currently reveal no statistically significant differences between the age, sex, and age-sex distributions of the combined Rongelap-Ailingnae group and the comparison population. Statistical analysis also shows an equivalent but fortuitous similarity between the Utirik and comparison groups. Scopeof the Medical Program Participation in the Brookhaven National Laboratory medical program is voluntary for both exposed and unexposed Marshallese. The program itself, however, which Brookhaven National Laboratory is under contract to the Department of Energyto carry out, is currently mandated by Public Law 95-134. Its expressed purpose is to’ provide ‘care and treatment” of radiation-related disease in the exposed population. No such etiologic distinction is made in actual medical practice, however. Thereis, of course, particular attention paid to thyroid neoplasia, as over the years that is one disease category clearly associated with the high radiation exposure of some of the Marshallese. In addition, surveillance for possibly radiationrelated disease is undertaken because the exposed population must be considered at increased risk for such disorders. For example, when a prolactinoma was diagnosed in an exposed womanin 1981, sera from virtually all exposed persons were tested for the presence of hyperprolactinemia (see below), This extra dimension in medical surveillance does not detract from primarycare coverage. Itis through the provision of comprehensive medical coverage that unpredicted effects of radiation exposure can be effectively disclosed. Thus the medical program continues to address a wide variety of health matters. Updatingof children’s immunizationsis a regular part of the medical team visits to Rongelap and Utirik. This is done in conjunction with a public health nurse from the Republic of the Marshall Islands Health Services. An intestinal helminth control program begun in 1978 was continued through 1982. Clinical care of diabetic patients now includes routine determinations of hemoglobin Ai- levels. An attempt at