By X-ray detection 25Fe 0.04 pCi/g or less By alpha detection 239,240, 0.02 pCi/g or less RESULTS Data are presented for the results of the analyses of the samples collected by LRE in the Marshall Islands in 1974 and 1975 and on Christmas Island in 1975. Appendix Tables 1 through 37 give the data for single samples. Tables 3 through 6 and Figures 3 through 7 in the text present Summarized data usually in the form of the mean + 1 standard deviation for several samples. The data will first be presented atoll] by atoll and wil] then be summarized by comparisons between atolls by selected sample types. All data are given as picocuries per gram of dry weight, except where expressly noted. Christmas Island The sites at which samples were collected in August, 1975, are shown in Figure 2. Samples were analyzed for gamma-emitting radionuclides only. Seven- teen naturally occurring or fallout radionuclides were detected in the samples analyzed, but only naturally occurring 40K and 238U, and the fallout radionuclide 137Cs were present in more than 20% of the samples. Values for these three radionuclides are given in Append ix Tables 1 (plants), 2 (fish and invertebrates) and 3 (soil). Usually 49K was the most abundant radjgnuclide ina sample and of the eleven fallout radionuclides detected only 3/Cs5 was present in concentrations greater than 1 pCi/g. Levels of 3/Cs above 1 pCi/g occurred only in Scaevola leaves (5.7 pCi/g) and unidentified leaves (32 pCi/g) from plants collected near the airfield wash-sump and in bone (1.6 pCi/g) from bonefish taken off London. The airfield wash-sump was used during the Dominic test series in 1962 to receive the wash-down water from aircraft used to collect air samples from the radioactive clouds produced by the detonations. The results of these analyses indicate,as noted by Seymour (1975),that “only trace quantities of fallout radionuclides are present at Christmas Island and the amounts are significantly less than the naturally occurring radionuclides." Kwajalein and Wotho Atolls Samples from Kwajalein and Wotho atolls were collected incidental to a trip to Bikini Atoll in April 1975. Results of the analyses of these samples of plants, soil and coconut crabs for gamma-emitting radionuclides, 90Sr and 239,240Py are given in Appendix Tables 4 (Wotho), 5 (Kwajalein) and 6 (Kwajalein coconut crabs). Naturally occurring 40K is the most abundant radionuclide present in the plant samples. Concentrations of 40K in pCi/g (dry) weight had 12 and 15 pCi of 137Cs/g. Strontium-90 levels were less than 1 pCi/g and ranged from 2.4 in breadfruit leaves from Wotho to 40 in coconut milk from Rigej Island in Kwajalein Atoll]. Cesium-137 was the predominant fallout radionuclide. Most plant tissues had between 0.5 and 2.5 pCi of 37Cs per gram of dry weight. The seeds and rind of a papaya fruit from Wotho Island 239,240py values ranged from 0.03 to less than 0.002 pCi/g in plants from both atolls. Soil levels were slightly higher with a maximum of 0.16 pCi/g