[en] Microscopic and photographic studies were conducted in 1972-73 at ABCC in Hiroshima on the morphology of superficial blood vessels of A-bomb survivors to determine whether the somatic effects of radiation still existed 30 years after the A-bomb. Control curves representing the relationship between age and score values assigned to morphological changes of the minute blood vessels of the fingernail fold, labial mucosa, and lingual mucosa, which could be regarded as an index of aging, were obtained. These were compared with similar curves obtained from A-bomb survivors with the aim of evaluating the effect of radiation on the aging process of these vessels. The late somatic effects of irradiation which were demonstrated 10 years after the A-bomb in a previous study (1956-57) were found to persist in the current study (1972-73) conducted 30 years after the A-bomb though not as pronounced as in the earlier study. A significant effect was observed only in the fingernail fold of those exposed to 100 rad or more under the age of 10 at the time of the bomb. A statistically significant difference was not observed for labial mucosa and lingual mucosa because the number of cases available for scoring was small, but a trend was observed for abnormalities of these two sites to be higher in frequency in the 100+ rad group under the age of 10 ATB than that of the control group. No significant difference was observed between the control and exposed with regard to radiation effect on the aging process using the relationship of score values to age as an index of aging. This is in accord with results of studies of A-bomb survivors which suggested that radiation induces life shortening attributable primarily to cancers, but not a general acceleration of the aging phenomenon. (author)