are ideal for measuring the faunal and floral contamination of a marine environment. The favorable climate, warm water, freedom from severe storms, protected waters of the lagoon, abundance of aquatic life of great variety, all contribute to their desirability as a base of operations. Another advantage is the fact that the atolls are isolated from other land masses with the result that repopulation of these areas from the outside does not confuse the interpretation of the data. The natural history of Bikini and Eniwetok Atolls has been thoroughly studied and reported upon. During the testing program of the past six years the living forms, the geology, the currents, and the weather have been studied in detail. The three expeditions to Eniwetok by staff members of this Laboratory for study of residual radiation have provided a backlog of information and developed skills that will be invaluable to any continuation or expansion of the study. Definition and Outline of the Problem The present program of study at Bikini-Eniwetok may be divided, for convenience, into three phases: 1. Pretest evaluation of contamination at Eniwetok. 2. Resurvey of Bikini Atoll. 3. Posttest evaluation of biological contamination of Eniwetok.