[en] The Annual Report of April 1987-March 1988 provides the information on up-to-date research activities of the National Institute of Radiological Sciences (NIRS) in Japan. Researches undertaken in the NIRS aim at promoting medical application of radiation and at investigating health effects of radiation and radiation protection. The research scope is therefore widely ranging from physics to genetics and from environmental science to clinical medicine. In addition to basic researches carried out by 14 research divisions, the following three longterm projects which were organized by scientists recruited from several divisions are currently in progress: (1) stochastic effects of radiation and risk estimation; (2) assessment of human exposure to environmental radiation; and (3) medical use of accelerated heavy ions. Projects (1) and (2) were finalized in this fiscal year. This volume is divided into the following scientific categories for ease of reader's understanding: physics, chemistry, biochemistry and biophysics, cell biology, immunology and hematology, pathology and physiology, genetics, clinical research, and environmental science, covering a total of 93 titles. Activities of each research division and organization of the NIRS are given in Appendices. (N.K.)