Six oligomers of -aminocaproic acid (ACA) from dimer (K2) to heptamer (K7), gamma-irradiated in an oxygen-free atmosphere, were investigated by the EPR method. The oligomers were synthesized and irradiated with60Co gamma-rays in the dose range from 0 to 6.5 kGy. The formation of –CH2–CONH–CH–CH2– radical was established. The quantitative determinations of total concentrations of spins were carried out. On the basis of the present and earlier results, the competition of the reactions of detachment of hydrogen and of breaking of –CONH– bond is discussed. The particular resistance of amide bond in dimer seems to be confirmed by the measurements of kinetics of radical decay. The mass spectrometry of gamma-unirradiated ACA and ACA oligomers K2-K4 was carried out. The results indicate a minute contribution of ionic processes in the radiolysis of ACA oligomers in solid phase.