same as 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 in controls, but still low. B. Clinical and Laboratory Findings 1. General Symptoms and Signs Soon after the initial exposure most of the fishermen experienced anorexia, fatigue, and lachrymation, and some experienced nausea and vomiting. 2. Skin Lesions Skin lesions were caused by beta irradiation. Shortly after the exposure, erythema appeared, which was followed by edema, vesicle formation, erosion, ulceration, or necrosis. Epilation was observed in 20 cases, becoming complete in the two cases who did not wear hats during the ash fall. The skin lesions were similar to ordinary radiodermatitis histologically. The skin injuries recovered gradually. At present, 25 years after the exposure, a few cases show depigmentation, pigmentation, and capillary dilatation. Atrophy of epidermis with narrowed stratum granulosum was noted in histological sections of these areas examined 10 years after the exposure. 3. Hematology a. Leukocytes: The total number of leukocytes decreased gradually, showing minimum counts at 4 to 8 weeks. Five cases revealed a count of <2000/mm3; 13 cases, <3000, and 5 cases, <4000. In one case, the leukocyte level was depressed to 800. A correlation was found between these minimum counts and the external gamma dose of each individual. At first lymphopenia was noted, and then neutropenia became marked. After 8 weeks recovery was noted, In many cases remarkable eosinophilia was observed at that time. In some cases immature neutrophils appeared in peripheral blood to a slight degree. b. Erythrocytes: In severe cases slight anemia was observed, accompa- nied by the depression of reticulocytes. Color indices were >1.0. The Price-Jones curves of erythrocyte diameter were displaced to the right of nor- mal at first, but returned to almost normal after one year. c. Platelets: Platelet counts showed increasing depression, reaching a minimum at 4 to 7 weeks (15,000 to 100,000/mm3). Slight coagulation dis- turbances were observed in a few cases. d. Bone marrow: In severe cases bone marrow was highly hypoplastic at the critical stage, followed by a general increase in cellularity. Recovery was not complete even after a year. At the recovery stage coexistence of hypoplastic and hyperplastic areas was observed in histological sections. e. Morphological abnormalities: Several morphological abnormalities, e.g., abnormal granules in lymphocytes or neutrophils, vacuoles in various leukocytes and megakaryocytes, giant nuclei and hypersegmentation of neutrophils, binuclear lymphocytes, abnormal mitosis of erythroblasts, etc., - 137 -