a wa mee a aateneins Selita 13 Acknowledgements We express our gratitude to the Shizuoka prefectural and the Yaizu municipal authorities ' We are deeply grateful to many agencies and individuals for valuable assistance to the medical survesxs since 1954, Many staffs of the National Institute of Radiological Sciences, particularly Dr. K. Tsukamoto, and Director, Dr S. Tanaka, Dr. S. Miwa, Dr. M. Seki, also to Miss .A. Yamane. Mrs. T. Kamagata, Mr. Dr. T. Yoneyama. Dr. E. Tazaki, Dr. Y. Mochizuki, Dr. S. Oryu, Dr. N. Saeki, Mr. M. Uchiyama, Mr. T. Tinuma, were most helpful in supporting the 1964 survey. Miura and Dr. M. Shimada, Dr. S. Ishii, Dr. I. Suzaki and other staffs of Yaizu City Hospital were also helpful in the medical survey. 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 Mrs. Y. Nakajima for laboratory studies. We wish to thank Dr. C. L. Dunham, U. S. AEC and Dr. R. A. Conard, Brookhaven National Laboratory, for arranging the visit of Dr. Kumatort to Marshall Islands.