In marine organisms collected a few weeks, months or years after fallout at a time when radiostrontium and other long-lived fission products would be expected to be present, radiostrontium has not been detected by the techniques used or is present at extremely low levels (Table 2). For conditions of equal fallout the sr? °_calcium ratio which is the important factor in determining the hazard from sr?° is a good deal less for pelagic fish than in such calcium-rich terrestrial food products as milk (Schaefer, 1958). Although radiostrontium may not be present in marine organisms collected in the vicinity of the Eniwetok Test Site, radiostrontium is found in some of the plants and animals living on the atolls in the same area. From the limited information avail- able at the time of the 1957 Hearings the inference was made that the plants and animals living on the coral atolls would not be expected to concentrate radiostrontium because of the high calcium content of the soils, the ocean. However, a situation similar to that which occurs in this is not true as some land plants and animals do accumulate sr?° in measurable amount s--especially the coconut crabs (Held, 1957). Although calcium is abundant in the soils apparently only part of the calcium is in a chemical form which is available to the plants. This is a difficult matter to resolve in a quantitative manner but efforts are continuing in