and Seymour (1963) reported an average 60 . Co concentration of 0.68 pCi.g wet in the liver of eleven .tuna from the Central wane Pacific. . 60 . We found no detectable Co in tuna from the Japanese fishery in 1°67 and 1°68, but did find significant concentrations of 60 . . tas ong . Co in yellowfin tuna collected near Bikini Atoll in 1969, _ Tt appears that the source of the atoll. 60 . . Co in these yellowfin tuna was This is consistent with Welander's (1967) report of ‘ as _ - 60 : . , relatively high concentrations of Co in marine organisms at Bikini Atoll in 1964, 330 pci/e dxy. average 9 . 2 lagoon contained Liver of fish from different islets in the 0 Held (1971) a . Co concentrations ranging from 79 to reported values as high as 260 pCi/g dry in fish livers collected at Bikini in 1969. of 0 If the source Co for the yellowfin tuna sampled is indeed Bikini Atoll, it would appear that the tuna stay in the vicinity cf the atoll for an appreciable period of time. It would be pertinent to investigate Bikini and Eniwetok Atolis, 1958, sites of nuclear and thermonuclear tests from 1946 to as possibly significant point sources, essentially, of radionuclides in the North Equatorial Current. Cesium-137 concentrations in the Pacific tuna, including those from the Bikini area, were of the same order of magnitude as the values reported by Seymour (1965), 3 (1967) and by Folsom and Young average valucs of 0.03 to 0.09 pCi/g wet muscle tissue.