¥ INTRODUCTION This is the 16th report of the Marshall Islands Medical Program prepared by Brookhaven National Laboratory (BNL). The purpose of these publications is to disseminate information concerning the medical status of 253 Marshallese exposed to fallout radiation in 1954. In so doing, the medical program is fulfilling a commitment incumbent onall health care organizations; i.c., to disclose in a timely fashion unique medical information relevant to the public health. Details of the BRAVO thermonuclear accident that caused the exposure have been published, and a 1955 article in the Joumail of the American Medical Association describing the acute medical effects in the exposed population remains a definitive and relevant description of events (Cronkite et al., 1955). Participation in the Marshall Islands Medical Program by the exposed Marshallese is voluntary. Throughout the 36 years of this program, each participating exposedindividual’s relevant medical findings, laboratory data, and disease morbidity and mortality have been published in the Brookhaven reports in a manner preserving patient confidentiality. Also, in each report, there has been an attempt to interpret these findings and to infer the role of radiation exposure in their development. But an equally important aspect of the reports has been presentation of the actual data so that readers can apply their own analyses to questions pertaining to the medical consequencesof the Marshallese exposure. EXPOSURE GROUPS The exposed Marshallese population originally was comprised of 64 persons on Rongelap Atoll whoeach received an estimated 190 cGy of wholebody external gammaradiation, 18 on Ailingnae Atoll (Sifo island) who each received 110 cGy, and 159 on Utirik Atoll who each received 11 cGy. In addition, there were 12 women who were pregnant at the time of the accident (3 on Rongelap, 1 on Ailingnae, and 8 on Utirik), each of whom received whole-body doses equivalent to others in the sameatoll, The twelve individuals exposed in utero became a part of the exposed population after birth. Because of radioiodines in the fallout, the thyroid gland received an exposure that was much greater than the whole-body dose, the magnitude of which was a function of age at the time of exposure (Lessard et al. 1985). In December 1991, the number of surviving exposed persons was: Rongelap - 48, Ailingnae - 11, and Utirik - 100. For most purposesin this report the Rongelap and Ailingnae groups are treated as one and referred to as the Rongelap group, because those persons exposedto fallout on Ailingnae were Rongelap inhabitants temporarily residing on this nearbyatoll. The Marshall Islands Medical Program also examines a comparison group that dates from 1957 when 86 unexposed people from Rongelap were selected. The makeup of the group approximated, in age and gender, that of the exposed Rongelap population (Conard et al., 1958). In December 1991, 56 persons remained in this group. From 1962 to 1978 additional persons were added as a second comparison group in order to supplement and replace persons lost from the original group. This group was also matched by age and genderto the exposed population and was similar to the 1982 Rongelap and Utirik exposed groups. In December 1991, the total population of the two comparison groups was 115. As in previous reports, it is the expanded unexposed population that is used in this report for comparisons of year-to-year medical events and for causes of death; this provides baseline prevalences of disease in the community from which unexpected consequencesofthe fallout exposure can be identified. They are also used to comparesurvival rates of the exposed population to the unexposed population. THE MARSHALL ISLANDS MEDICAL PROGRAM Policies: The mandate of the program, as formulated by the U.S. Congress most recently in 1980 (PL 96-205, . Sec. 106 (a)), specifies "...a program of medical care and treatment....for any injury, illness, or condition which may be the result directly or indirectly of such nuclear weapons testing program.” Subsequently, in 1985, the Compact of Free Association between the U.S. and the Republic of the Marshall Islands provided for radiation injury compensation to be managed by the Marshallese themselves. However, a subsidiary agreement, in