population; (2) remaining residua of the beta lesions of the skin; and (3) low levels of remaining radioisotopes absorbed internally, Late effecta of radiation exposure have not been seen, but certain of the more fundamental of these effects that have been observed in aninals and to a lesser extent in man will be mentioned in relation to the Marshai~ lese. 1. Shortening of life span (2,3,6) has not been evident, The 3 deaths that have occurred in the exposed population do not appear to indie cate a higher mortality rate than seen in the comparison populations. From these observations it would appear that some of the higher estimates of life shortening per roentzen may be too high. 2. Premature ageing (1,4,7,14) is difficult to assess. From obser- vations over the past 4 years the impression is that the exposed people have neither aged faster nor appear older than similarly aced unexposed Marshal- lese. No doubt the subtle changes which occur with ageing would be diffi- cult to detect over this period of time. During the 4 year survey, data has been collected in an attempt to obtain semi-quantitative estimates of biological age by scoring the degree of certain criteria such as greying of the hair, skin looseness, skin retractility, arcus senilis, retinal arteriosclerosis, accommodation, blood pressure, etc. These data have not been completely analyzed yet. 3. lezenerative diseases have not been found to be increased in the exposed people. No malignancies have been detected. In the irradiated Japanese an increased incidence of leukemia has been noted.(17,18) There have been no cases of leukemia or leukemic tendency noted in the Marshallese, (No cases have shown decrease in alkaline phosphatase of neutrophiles nor have increased levels of basophiles been noted.) Since the incidence of malige nancy or leukemia would be expected to be relatively low with the dose of wipe