composition of two samples has little meaning unless the age of the radioisotopes in the samples is approximately the same. Thirdly, the comparison of results of analyses may require that the samples be alike as to species, tissue and even physiological function. Using the giant clam again as an example, there are species living in the tropical Pacific that acquire a large portion of their food by growing and harvesting Zooxanthellae within their own body. These clams have a large and specialized kidney which concentrates radiocobalt to a high degree. There are other giant clams in the Pacific that are not as dependent upon Zooxanthellae and do not have as specialized a kidney. In the clams with the less specialized kidney more radiozinc is found than radiocobalt and this finding is in agreement with laboratory experiments with less specialized clams (Chipman, 1958). Thus itwould be inaccurate to make a generalization about the uptake of fallout radioisotopes by clams based upon the analysis of the unusual kidney of a highly specialized species which is common and important in only a limited part of the world. The comparison of results of radiological analysis of marine organisms may be used to evaluate the health hazard to man associated with eating certain sea foods. (Man‘s concern about fallout in the ocean is primarily as to how it will affect his health and secondarily as to how it will affect his ocean resources). The health hazard problem will not be discussed here, other than to