Average external gamma readings of the northern and southern Rongelap islands were 5.8 and 0.7 mr/hr respectively. The fish caughtoff Eniwetak Island (0.7 mr/hr external gamma) and Utirik Island (0.14 mr/hr external gamma) contained the same average concentration of internal activity as the fish of the southern Rongelap lagoon. Likiep fish (0.04 mr/hr external gamma on the island) contained lower but still detectable amounts of internal radioactive contamination. The total activity in the smaller fish (<150 g) was in general somewhat higher per unit body weight than that of the large fish. Crabs, clams, and especially snails were found to incorporate radionuclides to a much greater extent per unit body weight than did the fish in the corresponding localities (Table 4.3). A number of tissue samples of marine Specimens and of the rooster were analyzed for the concentrations of individual radionuclides (Table 4.5). In muscle and viscera samples of the animais from Rongelap, Utirik, and Rongerik, Sr®? contributes approximately 0.5 per cent of the total beta activity. Sr? is present in an approximately 1:1] ratio with Sr®9, Since the Hunter and Ballou calculations? indicate that Sr°? and Sr” each contribute about 2 per cent of the total beta activity at one year after fission, there does not appear to be any fractionation of radiostrontium into the soft tissues. As expected, most of the internally deposited radioactivity was found in the skeleton. Tissues of a few marine specimens*were analyzed for Cs'3? (37-year half-life) since this nuclide was present in high concentrations in water and coconut milk from this area. The tissues of the rooster and of the coconut crab contain significant amounts of Cs!37. A very high fraction of Cs!3" activity was noted in the muscle of the rooster (40 per cent of the total beta). Further radioanalysis of marine specimens indicated that the rare earth group constituted a few per cent of the total beta activity. Ru!$_Rn'% and Zr_-Nb® contributed the largest percentage of the total beta activity. Comparison of the fish and clams collected at one year post RQR ARCHIVES tion with those collected at one month post-detonation and analyzed 4 months post-detonation reveal the following differences. Inthe group collected at one month the concentration of internally deposited fission products was 5 to 10 times that of the fish collected at one year. The residual activity in the fish analyzed at 4 months post-detonation averaged 2.5 pc beta activity (Co8? equivalent) and the beta-to-gamma ratio was 1:2. Inthe current analyses, fish of comparable size hada beta activity of approximately 0.1 pe and a beta-to-gamma ratio of 1:4. The largest fraction of the gross beta activity in fish collected at one month was contributed by material in the viscera and liver. Smaller but equal amounts of activity were found in the muscle and skeleton in these fish. In the fish collected at one year post-detonation, in contrast to the group collected earlier, about 50 per cent of the activity was incorporated into the skeleton with only about 10 per cent found in muscle, -2)]-