-23- clear that the chief radiological concern at early times following an explosion will be those of total body radiation from gamma rays and skin irradiation from beta emitters. Except for the development of thyroid abnormalities and slight growth retardation in some exposed children, overt evidence of late effects of exposure have been minimal in the Marshallese. General health and disease incidence have remained about the same in the exposed and unexposed populations with no clear cut effects noted on mortality, birth rate, longevity, aging, incidence of malignancy and degenerative diseases or opacities of the lens. A few other positive Findings appear to be associated with their exposure such as an increase in miscarriages and stillbirths in the exposed women during the first 4 years after exposure, a lag in complete return of peripheral blood counts to the unexposed levels during the decade after exposure and the persistence of a low level of chromosomal aberrations at 10 years post exposure. The most important late findings have had to do with growth and development in the exposed children and the development of thyroid abnormalities. Slight retardation of growth has been noted mainly in the boys exposed at less than 12 years of age first noted a few years after exposure. Since 9 years post exposure thyroid nodules have developed in 17 cases and thyroid deficiency in 2 cases({all but.3 of these were in children exposed at less than 10 years of age). These effects are believed to be related to injury of the thyroid gland from exposure to radioiodines and gamma radiation at the time of the fallout. The detection of thyroid damage was hindered by its slow onset and due to the fact that the true PBI levels were masked due to the finding of elevated levels of iodoprotein in the Marshallese people. Thyroid surgery revealed that all nodules were benign except for 1 exposed adult 5001320