Preface and Acknowledgments THE UNDERTAKING of 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 Radiologieal Defense Laboratory. From the former, four medical officers, E. P. Cronkite, R. A. Conard, N. R. Shulman, and R. 8S. Farr were obtained. Two Medical Service Corps officers, W. H. Chapman and Robert Sharp, were also ob- tained from the sameinstitution. In addition, six enlisted men, C. R. Sipe, HMC, USN; P. KX. Schork, HMC, USN; C. P. A. Strome, HMC, USN; W. C. Clutter, HM, 1/C; R. E. Hansell, *Now Surgeon General, U.S. Navy. Iv HM 1/C; and J. S. Hamby, HM, 2/C were provided. From the United States Naval Ra- diological Defense Laboratory, one civilian physician, Doctor V. P. Bond; one medical service corpsofficer, Lt. Com. L. J. Smith; and four enlisted men, W. H. Gibbs, HMC, USN; J. C. Hendrie, HM, 1/C; W. S. Argonza, HM, 2/C; and J. Flannagan, HM, were supplied. The Division of Biology and Medicine, Atomic Energy Commission, sent two civilian physiclans, Dr. C. L. Dunham then Chief of the Medical Branch and Dr. G. V. LeRoy, Con- sultant and Special Representative of the Di- rector of the Division. The Armed Forces Special Weapons Project supplied one Army medical officer, Lt. Col. L. E. Browning, MC, USA. All personnel were experienced in the study of radiation injury: The preliminary studies performed by the Medical Department of the Naval Station at Kwajalein were under the direction of Commander W. 8. Hall, MC, USN, the station medical officer and his small staff who are to be commended for an excellent job. Upon arrival of the medical team, it became quite evident that, because of the large numbers of radiation casualties and the huge amountof work involved in collecting data, that primary responsibilities for various phases of the study would have to be delegated in order to obtain the necessary information for biological assay of the degree of injury. In the initial phase, hematological surveys and establishment of clinical records on each individual were emphasized. Dr. V. P. Bond organized and analyzed the results of the daily blood studies. Lt. N. R. Shulman, MC, USN, with the capable assistance of Mr. John Tobin, anthropologist of the Trust Territory, and Kathleen Emil, Marshallese nurse, as interpreters, undertook the establishment of medical histories and initial physical examinations. As the clinical picture