Preface and Acknowledgments THe Unperraxrneof the care and study of the human beings accidentally exposed to fallout radiation following the March 1, 1954, nuclear test detonation in the Pacific represented the first instance in which study of a large group of irradiated human beings was possible soon after exposure. Although the physical estimates of dose received by the individuals exposed to fallout radiation were thought to be sublethal, precise knowledge of the relative sensitivity of human beings to penetrating ionizing radiation was lacking. Accordingly, in addition to the initial medical team, provisions were made for a second echelon of specialized personnel in case they were needed. A preventative medicine unit of the Commander-inChief, Pacific fleet, was alerted for possible bacteriological studies; blood bank personnel, and additional clinicians and nurses were notified in case conditions justified their services in the Kwajalein area. Rear Admiral Bartholomew Hogan, MC, USN, Pacific Fleet Medical Officer,* promised full support of all the medical facilities of the Pacific Fleet were they deemed necessary. With the preceeding planning it was felt that any medical problem, regardless of the severity, could be promptly and adequately handled in thefield. The personnel for the team were obtained within the continental limits of the United States from the Naval Medical Research Institute and the United States Naval Radiological Defense Laboratory. From the former, four medical officers, E. P. Cronkite, R. A. Conard, N. R. Shulman, and R. 8. Farr were obtained. Two Medical Service Corps officers, W. H. Chapman and Robert Sharp, were also obtained from the sameinstitution. In addition, six enlisted men, C. R. Sipe, HMC, USN; P. K. Schork, HMC, USN; C. P. A. Strome, HMC, USN; W. C. Clutter, HM, 1/C; R. E. Hansell, *Now Surgeon General, U. 8. Navy. Iv HM 1/C; and J. S. Hamby, HM, 2/C were provided. From the Un States Naval Ra- diological Defense Lab$ratory, one civilian physician, Doctor V. P] Bond; one medical service corps officer, Lt. Gom. L. J. Smith; and four enlisted men, W. Gibbs, HMC, USN; J. C. Hendrie, HM, 1/C4W. S. Argonza, HM, 2/C; and J. Flannagang HM, were supplied. The Division of Biology {nd Medicine, Atomic Energy Commission, ser two civilian physiclans, Dr. C. L. Dunhafn then Chief of the Medical Branch and Dy G. V. LeRoy, Con- sultant and Special Repfesentative of the Di- rector of the Division. The Armed Forces Special Weapons Project supplied one Army medi- cal officer, Lt. Col. L. E. Browning, MC, USA. All personnel were expq@rienced in the study of radiation injury: The preliminary studges performed by the Medical Department of fhe Naval Station at Kwajalein were under the direction of Commander W. S. Hall, , USN, the station medical officer and his sfnall staff who are to be commended for an excpllent job. Upon arrival of the mddical team, it became quite evident that, becaus§ of the large numbers of radiation casualties angl the huge amount of work involved in collectigg data, that primary responsibilities for varios phases of the study would have to be delegated in order to obtain the necessary informatiog for biological assay of the degree of injury. In the initial phase, hematological surveys and establishment of clinical records on each inflividual were emphasized. Dr. V. P. Bondj organized and ana- lyzed the results of the daily blood studies. Lt. N. R. Shulman, MC, U§$N, with the capable assistance of Mr. John T the Trust Territory, and shallese nurse, as interpfeters, undertook the establishment of medicalf histories and initial physical examinations. As the clinical picture