The cascade damage and its kinetic behavior in various kinds of ceramics irradiated with fission- and fusion-neutrons have been examined through transmission electron microscopy. Fission- and fusion-neutrons introduce relatively dilute concentration of point defects around primary knock-on atoms through the displacement cascade process in low-Z ceramics. Higher concentration of point defects, which induces the contrast corresponding to the cascade damage though TEM, is induced only in covalent crystals consisting of relatively high-Z elements. The nucleation and growth process of interstitialloops is strongly affected by the crystal structure and structural vacancy.