The accumulation of paramagnetic defects in KClO4 crystals during x irradiation at 26 K has been studied by ESR. The dose dependence of the yields is described in terms of processes involving already formed radiation-induced defects. A kinetic analysis of a post-irradiation reaction between ClO42- and (ClO4)2- defects reveals a marked spatial correlation between the defects, which stems from the initial pattern of energy deposition. Our results indicate that recombination of holes and electrons occurring during the irradiation proceeds via unstable configurations of (ClO4)2- and ClO42- in a process analogous to the observed post-irradiation reaction. © 1979 The American Physical Society.