external radiation dose was approximately 170-600 rad for I4 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 20-129 rad. Urine samples which were collected at 4 weeks after the explosion revealed signilicart amount of radioactivity. However, the radioactivity decreased rapidly, ¢.y. at about 6 months post detonation the activity was barely detectable. In the analysis al-cer 8 1/2 years and 10 years the levels of 3764 and 905, in urine were the samic 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 cxperienced anorexia, fatigue, and lachrymiation, and in some cf them nausea and vomiting occurred. 2. Skin lesions Skin lesions were caused by beta irradiation. Shortly after the exposure, they suffered from erythema which was followed by cdema, vesicle, crosion, ulecration 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 radiodcrmatitis nistolowically. uradually. Epilations were observed The skin injries recovered Ac present, namely 20 years after the exposure, ina few cases depigmentation, pigmentation and capillary dilatation are observed. Atrophy of cpidermis with narrowed stratum granulosum were clear . 4 in histolugical section of these arca cxamined 10 years after the exposure. 3. a. Hematology Leukocytes : Total number of leukocytes decreased gradually, - 90 - 7