[en] The study on radiation damage under severe irradiation condition has been developed in connection with the materials for fusion reactors. This paper is a report of a study meeting concerning the radiation damage. The free migration of interstitial atoms is discussed on the basis of the measurement of internal friction. The point defects of pure iron irradiated by reactor neutrons at low temperature, the 304 stainless steel and FeSiB amorphous alloy irradiated by He ions at room temperature were studied by the measurement of Moessbauer effect. The study on radiation defect by X-ray diffuse scattering is reported. Discussion on the lattice defects in insulating crystals is presented. Sputtering by high density electron excitation, and the behavior of T, D and H atoms in low temperature solids are discussed. Other topics presented in this report are neutron irradiated FCC metal crystals, the radiation effects on cadmium halide crystals and impurity metal ions, and the effects on the properties of semi-conductors by irradiation. The reports on the joint meeting of International Cryogenic Material Conference and Cryogenic Engineering Conference of U.S.A., and the IAEA meeting on the nuclear data for radiation damage and safety are presented. (Kato, T.)