13 Acknowledgements We are deeply grateful to many agencies and individuals for valuable assistance to the medical surveys since 1954. Manystaffs of the National Institute of Radiological Sciences, particularly Dr. K. Tsukamoto, Director, Dr S. Tanaka, Dr. S. Miwa, Dr. M. Seki, We express our gratitude to the Shizuoka prefectural and the Yaizu municipal authorities and to the Fishermen’s Cooperative Union of Yaizu for their arrangement for smooth operation of the survey. We are thankful to Dr. T. Iseki and Mrs. M. Sato for their excellent culture techniques, and also to Miss A, Yamane, Mrs. T. Kamagata, Mr. Dr. T. Yoneyama, Dr. E. Tazaki, Dr. Y. Mochi- Miura and zuki, Dr. S. Oryu, Dr. N. Saeki, Mr. M. Uchi- studies. yama, Mr. T. linuma, were most helpful in supporting the 1964 survey. AEC and Dr. R. A. Conard, Brookhaven National Dr. M. Shimada, Dr. S. Ishii, Dr. I. Suzaki and other staffs of Yaizu City Hospital were also helpful in the medical survey. Mrs, Y. Nakajima for laboratory | We wish to thank Dr. C. L. Dunham, U. 8S. Laboratory, for arranging the visit of Dr. Kumatort to Marshall Islands.