Experiments are reported on the production, and annealing kinetics of free radicals in irradiated organic crystals. Both processes are shown to be well reproducible for nominally identical crystals although the annealing rate may be much slower in crystals damaged by previous irradiation and annealing. Free radical destruction was found in numerous instances to proceed by second-order kinetics, the only exception being crystals of acetylglycine where the reaction is third-order. Activation energies of the reactions are reported together with experimental investigation of the deuterium isotope effect. The significance of these results is discussed in relation to the existence of hydrogen atom jumping of “Kenon diffusion” as and annealing mechanism.