[en] This report covers the period from April 1, 1981, to March 31, 1982, and the information on the research carried out by the staffs of the institute during this period is given. The total budget for the fiscal year 1981 was 5,038.9 million yen including personnel costs. Besides basic research, three long term projects have been carried on, i.e. the risk assessment on low level radiation, the research on the exposure to environmental radiation caused by nuclear facilities and others and the medical application of a particle accelerator. In connection with the project on the risk assessment of low level radiation, a new laboratory for the research on internal radiation effect has been under construction, and is expected to be completed in the fiscal year 1983. The biological effect of tritium has been adopted as a subtheme of this project. These three projects have progressed satisfactorily. In the report, the summaries of 10 papers on physics, 5 papers on chemistry, 9 papers on biochemistry and biophysics, 13 papers on cytology and morphology, 10 papers on physiology, 9 papers on genetics, 8 papers on immunology and hematology, 8 papers on medical studies and 17 papers on environmental studies are collected. (Kako, I.)