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 exposedto fallout radiation in 1954. In so doing, the medical program is fulfilling a commitment incumbenton all health care organizations; i.e., 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 Journal 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 exposed individual’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 exposurein 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 consequences of the Marshallese exposure. EXPOSURE GROUPS The exposed Marshallese population originally was comprised of 64 persons on Rongelap Atoll who each 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), cach 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 radioiodinesin 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 survi¥ing exposed persons was: Rongelap - 48, Ailingnde - 11, and Utirik - 100. For most purposes in th& report the Rongelap and Ailingnae groups are trdated as one and referred to as the Rongelap grohp, because those persons exposedto fallout on Ailfngnae were Rongelap inhabitants temporarily residing on this nearbyatoll. The Marshall Islands Medical Pybgram also examines a comparison group that dates from 1957 when 86 unexposed people from Rogpelap were selected. The makeup of the group approximated, in age and gender, that of the exposefl Rongelap population (Conard et al., 1958). Inj December 1991, 56 persons remained in this grdup. From 1962 to 1978 additional persons were [added as a second comparison group in order to fupplement and replace persons lost from the original group. This group was also matched by age anli genderto the exposed population and was similarko the 1982 Rongelap and Utirik exposed groups. In December 1991, the total population of the two fomparison groups was 115. As in previous repors, it is the expanded unexposed population thatis fused in this report for comparisons of year-to-yefr medical events and for causes of death; th provides baseline prevalences of disease in the F-ommunity from which unexpected consequences off the fallout exposure can be identified. They are aso used to compare survival rates of the exposed pq@pulation to the unexposed population. THE MARSHALL ISLANDS MEDICAL PROGRA Policies: . The mandate of the program, as forfnulated by the U.S. Congress most recently in 1980 Sec. 106 (a)), specifies "...a program of and treatment....for any injury, illness, of condition such nuclear weapons testing § Subsequently, in 1985, the Compact Association between the U.S. and the F the Marshall Islands provided for radiajion injury compensation to be managed by the Marshallese themselves. However, a subsidiary agrfement, in