Introduction In a previous report (No 76) describing the concentrations of specific radionuclides detected in the lagoon water of Kwajalein Atoll 167°40'E), it was concluded that the concentrations of (9°N 2394240, u and 137 Cs ~ “were similiar to the global tallout concentrations detected in north equatorial Pacific surface waters. However, samples of fish collected from Kwajalein Atoll in 1972 (Ne 73) contained concentrations of 23942405,| that were higher than levels in fish from other global regions contaminated only with global fallout debris. Another study had reported (Sc 75) that the concentrations of plutonium in convict surgeon fish collected from regions of Enewetak Atoll, one of the Pacific nuclear test sites used by the U.S. between 1948 and 1958, were not significantly different than levels in fish from the control station, Kwajalein Atoll. This was unexpected because during 1972, 1974 and 1976 the average concentration of 2394240, in Enewetak lagoon water (No 78a) was 60 to 190 times higher than the 1975 average Kwajalein lagoon water concentration of 0.45 + 0.21 pCi/m> (No 76). One is compelled to submit, based on these data, that the use of a concentration factor to relate plutonium concentrations in marine organisms to environmental concentrations seems highly questionable. Based on these 1972 plutonium concentration data (Ne 73) for eviscerated whole fish and the average concentration in 1975 Kwajalein lagoon seawater, the calculated concentration factors for the Kwajalein fish would range from 2 x 10° to 6 x 10°. These values are orders of magnitude larger than other reported (Ne 75, No 78b, He 75, No 72) concentration factors for plutonium in fish. Th e 2394240 Pu concentrations of eviscerated and whole reef fish from Enewetak Island of Kwajalein Atoll in 1972 ranged from 230-960 pCi/kg dry DOE ARCHIVES