Test Site. These were Castle - 1954, Redwing - 1956, and - Bardtack - 1958. MATERIALS AND METHODS The visits to the islands were made possible by the cooperation of Task Force 7.1 and the Trust Territory of the United States. Two to five-man teams were flown to the islands to collect samples which were refrigerated, to the Eniwetok Marine Biological Laboratory, weighed, dried, returned dissected, packaged and then sent to the Laboratory of Radiation Biology, sing and analysis. Seattle, Washington, for further proces- The samples were prepared on 1.5-inch stainless steel planchets and counted for gross beta radio-~ activity in either one of two counting systems operated in the Geiger-Muller region: (a) One and one-half-inch end- window "pancake" type Anton tube in a 3-inch lead Anton shield connected to a Nuclear Chicago Model 181 scaler and equipped with an automatic sample changer. This system has a background of about 18 counts per minute and an efficiency of approximately 12 per cent based on K40 , (b) An internal counting chamber continuously flushed with methane in a ~ Radiation Counter Laboratory Nucleometer Mark 9, Mode},34 Energy Departme: *s oifice Historian ARCHIVES