external radiation dose was approximately 170 - 600 rad for 14 days, about half or more being irradiated on the first day. The dose to each person differed depending on his behavior on the boat and the position of his cabin. The integrated dose to thyroid glands from 131, was inferred as about 20-120 rad. Urine samples which were collected at 4 weeks after the explosion revealed significant amount of radioactivity. However, the radioactivity decreased rapidly, e.g. at about 6 months post detonation the activity was barely detectable. In the analysis after 8 1/2 years and 10 years the levels of 1376, and 5, in urine were the same to those of normal Japanese. At the same time the results of whole body counting showed no significant difference between fishermen and controls. The radioactivity in several organs of the fatal case was higher than controls, but low. B. 1. Clinical and Laboratory Findings General symptoms and signs Soon after the initial exposure most of the fishermen experienced anorexia, fatigue, and lachrymation, and in some of them nausea and vomiting occurred. 2. Skin lesions Skin lesions werecaused by beta irradiation. Shortly after the exposure, they suffered from erythema which was followed by edema, vesicle, erosion, ulceration or necrosis. in 20 cases, especially 2 cases who did not wear hats during ash-fall revealed complete epilation. These skin lesions were similar to ordinary radiodermatitis histologically. gradually. Enpilations were observed The skin injries recovered At present, namely 20 years after the exposure, ina few cases depigmentation, pigmentation and capillary dilatation are observed. Atrophy of epidermis with narrowed stratum granulosum were clear in histological section of these area examined 10 years after the exposure. 3. a. Hematology Leukocytes : Total number of leukocytes decreased gradually, - 90 - 90 6b 1d