-23- Summary This report contains data and a discussion of the analysis of the radioactivity in the fish collected at Rongelap and Aillinginae Atolls during the summers of 1956 and 1957, as well as comparisons with previous radiobiological studies. Gross levels of beta radioactivity in muscle tissue ranged from .016 to .038 uc/kg wet weight; bone from .020 to . 102 uc/kg wet weight; and liver tissue from .059 to .727 uc/kg wet weight. Decline in radioactivity in the various tissues, as determined from data obtained from collections of fish made in 1954, 1955, 1956 and 1957, indicates recontamination from the nuclear tests of 1956. The levels of radioactivity in bone and muscle tissues during the summer of 1957 were approximately the same as they were in the summer of 1955. Data on gross gamma radioactivity indicated that about the same relative amount was present in the tissues of fish and in fish from different areas as was observed with gross levels of beta activity. Both gamma and beta radioactivity were higher in the liver tissue than in other tissues of the samefish, muscle tissue being the lowest of the materials tested. The radioactivity in the fish was lower at Rongelap Island than at either Enibuk Island, Ailinginae Atoll,or Kabelle Island, on the northeast rim of Rongelap Atoll. Of the three areas, Kabelle Island had fish with the greatest amountof radioactivity. DOR ARCHIE TS