throughout Micronesia, even though improvements in Living standards have occurred, the people are subject to frequent infections such as gastroenteritis, upper respiratory infections, skin lesions and intestinal parasites. Therefore it is not surprising that the gamma globulin leve ls in the Marshallese have been found to be elevated. people. The A/G ratio is reduced or reversed in most of the The serum protein levels are generally elevated and may in part be related to dehydration associated with tropical environment where dependence for water is on rainfall which is scant at certain seasons. We have noted that the specific gravity of the urine is frequently high, and reduced red cell and blood volume have been found in this population. In spite of these factors the present studies should be valid for comparison of the exposed and unexposed Marshallese populations, since both groups are generally exposed to the same environmental factors, and studies of genetically inherited characteristics show them to be a relative homogeneous population. These studies are believed to test the immunological status of the individuals to some degree though interpretation of some of the results: is not readily apparent. The discussion which follows will first consider. the results of the various tests in the unexposed population in terms of correlation with aging. The differences in the results in the exposed population will then be discussed in regard to radiation-induced effects. In regard to aging effects in the unexposed comparison population it is quite obvious from the various graphs that even in the tests showing changes more closely correlated with aging, that changes are maximum by middle years (usually in the 40-50 age group) with little or no change, or in some cases even slight reduction after middle age. 1 The reason