In addition to the whole body gamza exvosure and beta burns of the skin, a significant amount of radionuclides was absorbed by ingestion and inhalation. The dose calculations were begun at Kwajalein about two weeks after the detonation by determination of radioactivity within pooled urine samples. Such samples were returned to the United States for radiochemical analysis. Such analyses were continued and, at six months following the exposure, only minute amounts of radioactivity were detectable in the urine. Radioactive iodine was the most hazardous of the absorbed isotopes and, by extrapolation, a dose of 160 rads to the thyroid gland of the exposed adult and a range of 700-1400 rads to the exposed child's thyroid gland was received. In addition, both groups received 175 rads from external gamma irradiation. Articles on this subject, published by the U.S. Atomic Energy Commission, the Brookhaven National Laboratory, the Department of Defense, and testimony before the Special Subcommittee on Radiation of the Joint Committee on Atomic Energy, Congress of the United States, were carefully reviewed with particular attention to methods used in dose calculations. Granted that much of the data were determined by post-detonation calculations and extrapolations, one must conclude that the published figures are reasonably accurate. It may be possible to reevaluate the data but this would be a formidable procedure, By the Spring of 1957, ten surveys of Rongelap Atoll had been made by the Applied Fisheries Laboratory of the University of Washington and U.S. Naval Radiological Defense Laboratory. A decision was made to allow the people to return to their island on June 29, 1957, with the belief that permanent residence would not be detrimental to their health. The last nuclear device of the Operation Hardtack Tests was detonated ' on Eniwetok on July 26, 1958. Published data indicates that only a small and insignificant increase in background levels occurred on Rongelap as a result of this test. In early 1958, a joint field trip was made by the Laboratory of Radiation Biology of the University of Washington and the Brookhaven National Laboratory Medical Team. Subsequently, three additional radiation surveys were conducted by the Laboratory of Radiation Biology prior to 1960. The maximum gamma dose level in September of 1959 was recorded as 0.04 mrads per hour, or approximately 350 mrads per year, well within the accepted maximum permissible dose of 500 mrads 201 LO1uBIO