- CHAPTER l INTRODUCTION © The fallout on the Marshall Island atolls of Rongelap, Rongerik, Ailinginae, and Utirik from the first shot of the series beginning 1 March 195), created an initial emergency during which the gathering of data was of secondary importance, This fundamental fact has result- ed in uncertainty in all attempts to reconstruct the circumstances of the event, Calculation of the external doses received by the exposed _ Andividuals has required that available information be supplemented by assumptions, Much of the information itself was necessarily more indicative than exact. In spite of these difficulties, the cooperation of many individuals and groups made it possible to develop a fairly consistent estimate of external gama dosage, although the question of beta exposure must remain mostly unanswered. It has been assumed that no significant neutron or alpha particle exposure occurred, Tims, the main consideration in this report is the total body gamma radiation exposure, Internal doses from inhaled or ingested material have been discussed elsewhere (Reference 1), Data which form the basis of the analysis were furnished by sever‘al sources which are listed in the References, These represent measurements made both in the field and in the laboratory in the period immediately following the exposure, included wherever it was available, Later information has also been A summary of these results appears in Reference 16, which covers thé biological and medical aspects of thse incident.