When organic solids are subjected to ionizing radiation free radicals which often persist for long periods of time are generated. It is shown here that the free radicals in irradiated crystalline propionamide,n-butyramide, isobutyramide, and stearamide can react rapidly with oxygen, nitric oxide, and similar gases. Evidence has been obtained from electron spin resonance, X-ray diffraction, gas absorption, and end-product analysis that the gases diffuse into the crystalline lattice of the amides reaching the radical sites and initiating chain reactions which are influenced by the diffusion rate. The layer type crystal structure which is found in these compounds is important in understanding these effects.