II. A. GENERAL MEDICAL SURVEYS Background Following gradual resolurion of early radiation effects in exposed Marshallese, a program for their continuing care and observation was instituted under the aegis of the Atomic Energy Commission. A medical team, headquartered at Brookhaven National Laboratory and supplemented by a national corps of consultants, has continued to implement the program under the aus-— pices of the AEC and its descendant agencies (the Energy Research and Development Administration and the Department of Energy) with cooperative support from the Departments of Defense and Interior (Trust Territory of the Pacific Islands). From its inception, the primary objective of the Marshall Islands program was the early detection and treatment of any medical conditions that might evolve as a consequence of the radiation exposures. Such an objective required a longitudinal prospective follow-up study of exposed individuals along with an appropriate control population. Both scientific and humanitarian considerations dictated establishment of a field capability for administering periodic primary medical care with some mechanism available for secondary and tertiacy referral. In its practical application, complexity of this program. several unique problems contributed to the As noted in the Introduction, the Marshallese were exposed to a highly complex spectrum of radiations under source condicions that were unlike any generally experienced in previous radiotherapeutic, accident, or warfare situations. Dosimetry, therefore, became more a matter of estimation than precision, especially in regard to specific individuals (2). Accurate assessment of risks, morbidity, and mortality was complicated statistically by a number of problems. The sizes of the exposed populations were small. Data on the incidences of various diseases in Micronesia were meager or non-existent, and vital statistics were unreliable because of the lack of accurate record keeping in the islands. It was therefore necessary to include an unexposed comparison population ("control group’) in order to evaluate better the findings in the exposed populations. Difficulties associated with these groups are discussed below. [In addition to the above problems, geographic, logistic, cultural, and political considerations continually influenced implementation of certain aspects of the program. In the first decade following the accident, there were few clinical find- ings that could reasonably be related to radiation (1,13). Cutaneous scarring and depigmentation were the only residue of beta burns, and no evidence of skin malignancy appeared. Exposed Rongelap women may have had an increased incidence of spoataneous abortions, and some children exhibited growth retardation. Peripheral blood elements remained minimally below compari¢on means for about five years, and some chromosomal defects were detected. In the second decade, the development of hypothyroidism and thyroid nodules in a significant number of individuals and the occurrence of a fatal case of acute myelogenous leukemia heralded the possible onset of serious late irradiation sequelae. Aspects of these findings have been reported previously (1,33), and some are discussed in greater detail in Section VIII.A. Aside from these problems, the general health of the exposed Marshallese appeared to