Table 1. Location Bikini Atoll Bikini Lagoon Aomen-Yurochi Islet Aomen-Yurochi Islet Bokonejien Islet Bokonejien Islet Bokonejien Islet NamuIslet Eniwetok Atoll Japian Islet FElugelab Islet Belle Islet Bete Islet Rongelap Atoll Kabelle Islet Kabelle Islet Kabelle Islet Palmyra Island LEAD-210 IN SELECTED ATOLL SAMPLES Sample CollecCollecatop tion tion (d/m/g/ dry date depth(cm) wt) Sediment, Soil Soil Crater sediment Crater sediment Crater sediment Soil 1949 1967 1967 1964 1964 1967 1964 0-12 0-1 + 0-3 Q-12 G-12 0-12 13-16 6440-10 2-74 0-05 2-0 + 0-05 4:5 +0-07 4-1+0-05 3-34 0-04 0-5 + 0-02 Soil Crater sediment Soil Soil 1952 1964 1954 1954 0-1 Q-12 0-3 0-3 2440-05 3-8 + 0-06 0-7 40-03 0-440-02 Soil Soil Soil Soil 1961 1961 1961 1962 0-0-6 06-12 0-8 0-8 4340-08 1440-04 2-7 40-06 0-6 + 0 03 0-1-2:2 d/m **Ra/g dry coral, while concentrations in samples from depths of 60 m were 2-3 d/m ***Ra/g dry coral. The greater concentrations at depth result from ingrowth of 2?*Ra from the parent radionuclide, *U. In addition the concentration of #1°Pb in rainwater is approximately 5 d/m/l. (refs. 10 and 11). and therefore a reasonable estimate of the naturally occurring *}°Pb concentration in coraline soils is several d/m/g drysoil. My results, Table 1, show concentrations of 24Pb that do not exceed those expected to occur naturally. The =6Ra content of crater sediments and deep core sainples should be about the same, as they are. Soils would be expected to contain concentrations of #?*Ra of 0-1-2-3 d/m/g dry soil, depending on the depth sampled, the degree of equilibrium between 22*Ra and its parent, ?3*U, and the amount of particulate matter associated with the fallout; the latter is a mixture of coral from various depths and hence variable in 22*Ra content. Thomas'? reported the 207Bi content of the crater sediment collected at Bokonejien Islet in 1967 as 200 d/m/g dry sediment. By contrast, the 7°Pb content of the same sample is 3-3 d/m/g dry. If?°Pb had been produced in significant amounts during the testing programme, the concentrations in the crater sediments would be much greater than they are. It seems unhkely that the US tests of 1958-59 or 1961-62 contributed significantly to the #°Pb content of the atmosphere. Production by USSR tests cannot be discounted due to differences in structural materials in and around the device, but the absence of any reported 2077Bi in worldwide fallout associated with these tests casts some doubt on this possibility. I thank Professor E. E. Held for selecting the samples and for helpful discussions. Ehis work was performed under contract between the US Atomic Energy Coinmission and the University of Washington. T. M. BeasLey