[en] EPR and NMR evidence on the mechanism of accumulation of γ-irradiation induced defects in molecules has been obtained. Free radicals resulting from the initial radiation-chemical process take part in secondary radical reactions. Data on limiting concentrations of paramagnetic centres appearing by irradiation by particles with different ionization loss values and spur parameters can be helpful for solving problems connected with the effect of large irradiation doses on materials and with the efficiency of radiation destruction of low molecular and polymer compounds