ABSTRACT The final report of Project 4.1 contained detailed information concerning the clinical observations and therapy, the external lesions, the hematological studies, and the in- ternal radioactive contamination of the 62 native inhabitants of Rongelap and Ailinginae atolls who were exposed to radioactive fallout following the detonation of Shot 1 at Bikini on 1 March 1954. Eighteen natives. who were temporarily residing or visiting at Sifo Island (Ailinginae Atoll) 1-3 March are also listed. This addendum report contains the following supplementary data regarding these exposed Marshallese: (1) a detailed aketch of Rongelap Village; (2) a brief description of the islanders’ homes and theirfood and water supplies; (3) the various family groups and the location of their dwellings; (4) events during fallout: (5) the evacuation and de- contamination procedures; and (6) readings of the external radioactive contamination of these individuals. The majority of this material was obtained after the Marshallese were evacuated from their home islands (while they were under medical observation at Kwajalein). Additional information was obtained when either one or both authors accompanied radiological survey teams to Rongelap. These survey trips were made 26 March, 3 April, and 21—23 April 1954. Due to language interpretation difficulties, some of the material is incomplete or inaccurate and is subject to correction and revision by future survey teams. Twenty-eight American Military personnel stationed on Eniwetak Island, Rongerik Atoll, were exposed to radioactive fallout following the detonation of Shot 1 at Bikini on 1 March 1954. The onset of visible fallout material was observed at approximately 1400~1430 hours, 1 March. An ATN/3a Recording Dosimeter, located on the island (Eniwetak), gave first positive indication that fallout particles were radioactive. This instrument went off scale at 100 mr/hr at H plus 6 hours and 48 minutes. Authorities at Eniwetok were notified of fallout via dispatch. Personnel of Rongerik ' -were evacuated by plane to Kwajalein at 1246 and 1800 hours, 2 March. Following de- contamination procedures the men were sent to the infirmary at Eniwetok for clinical observation and preliminary clinical study. On 16 March, they were returned to Kwa- jalein and placed under care of the personnel of Project 4.1. The details of the clinical studies are presented in the final report of Project 4.1. The exposure of these individuals afforded a unique opportunity to study the effects of radiation in man and it was considered desirable to supplement the clinical studies | with as much information as possible concerning the period of exposure. Accordingly, these men were interviewed individually and asked to describe the fallout, their activities during the fallout, foods and liquids consumed, their clothing and housing, the disposition of film badges, etc. Insofar as possible, this information is recorded ver- batim in the present report. The report also includes a summary of these interviews, film-badge readings, and readings of the external radioactive contamination of the men Cc c qi before and during the decontamination procedures. tuba a