Results Gross Beta Radioactivity Table 1 shows gross levels of beta radioactivity in the fishes during July 1957. Of the three islands visited the highest levels were found in the fish liver tissue from Kabelle Island. In all cases, for comparable tissues, the least radioactivity was found in fish collected near Rongelap Island. Radioactivity in muscle tissue of fish from Enibuk Island, Ailinginae Atoll, was as great or greater than that of Kabelle Island. Comparatively minor differences are seen in the levels of radioactivity in similar tissues of omnivorousand carnivorous fishes from Rongelap Island, except for stomach contents. The presence of algae in the stomachs of many omnivorous fish would account for the higher levels in these fishes. Two species, the goatfish and the halfbeak, were taken in sufficient quantities for separate analyses. The goatfish feeds on small inverte- brates, principally crustacea, of the sandy bottom areas. Levels of radioactivity in the stomach contents and liver of these fish were much higher than in other fish of the same area; however, radioactivity in muscle tissue was not much higher. The halfbeaks from Kabelle Island had about the same amountof radioactivity as fish from Rongelap, reflecting, perhaps, a different feeding habit than that of other fish of Kabelle Island. The halfbeak normally feeds at the surface on macroplankton, <agqvEs wi We KY, ce