FOREWORD As part of the United States atmospheric nuclear weaponstesting program between 1946 and 1958, 23 nuclear devices were detonated at the Bikini Atoll and 43 nuclear devices were detonated at the Enewetak Atoll. A 1954 nuclear weapons test on the Bikini Atoll, test shot code named Castle Bravo, produced a nuclear yield much higher than anticipated. Thelevels and dispersionof the radioactive fallout from Castle Bravo weresignificantly greater than originally expected. This resulted in radioactive fallout on the inhabited atolls of Rongelap and Utrik. The Rongelap and Utrik people were evacuated from their contaminated atolls 48 and 72 hours, respectively, after the Castle Bravo test shot. The original population directly exposed to the fallout from Castle Bravo consisted of 241 individuals and 12 fetuses. Absorbed doseestimates for the exposed population were in the order of 0.11 to 1.9 Gray (11 to 190 Rad) to the whole body and from 1.9 to 200 Gray (190 to 20,000 Rad) to the thyroid. Public Law 99-239 mandated that the Government of the United States would “continue to provide special medical care and logistical supportto...the remaining population of the Rongelap and Utrik who were exposed to radiation resulting from the 1954 Bravo test." The Department of Energy (DOE), through its contract with the Brookhaven National Laboratory Medical Department, implements this congressional mandate. The present DOE Marshall Islands medical surveillance program consists of two field missions per year. The purpose of the program is to provide medical care and treatment for radiologically related problems for those Marshallese who were exposed to fallout from the 1954 Castle Bravo test. As of December 1991, the originally exposed population consisted of 159 individuals. The medical surveillance program offers, on a voluntary participation basis, an annual physical examination to these individuals, as well as annual physical examinations to a comparison/control unexposed population. The medical surveillance procedure includes a complete annual physical examination, which is based on the criteria established by the American Cancer Society. Typical medical missions included specialists in gastroenterology, hematology, obstetrics/gynecology, endocrinology, oncology, radiology, cardiology, nephrology, pulmonology, and rheumatology. This, the 16th report of the Marshall Islands Medical Program, disseminates information concerning the medical status of the 253 Marshallese exposed to the fallout from the 1954 Castle Bravo test shot. Director Office of International Health Studies Paul J.Seligmaé, M.D., M.P.H. Deputy Assistant Secretary for Health Studies