High resolution electron microscopy has shown that the morphology of radiation damage was similar for a wide range of crystalline organic compounds. The considerable lack of contrast suffered by halogenated compounds in regions of radiation damage seems to arise from preferential loss of halogen from these areas. This aspect of loss of peripheral atom from the molecule is also supported by results obtained by encapsulating the specimen between carbon and other films. The encapsulation reduced the effect of radiation damage and it is suggested that the encapsulation held the peripheral atoms in the crystal, which enabled them to recombine with ions and radicals formed by the damage and to prevent molecular degradation. A reaction mechanism based on this premise is proposed.