Summary The γ-pre-irradiation effect on the recombination of recoil cobalt atoms in some neutron irradiated crystalline cobaltic complexes was examined. The introduction of defects into the lattice by pre-irradiation seems to increase the initial retention and promotes the annealing phenomenon, though on the other hand radiolytic phenomena may also appear. Plots of isothermal annealing curves appear to indicate the existence of two or more parallel consecutive recombination-decomposition reactions. A kinetic interpretation of such mixed phenomena is also given. Complex kinetic phenomena also appear to be quite general in annealing processes for systems already studied by other authors. These systems, if examined in this light, may lead to a new interpretation as to the way in which recombination occurs during annealing.