A comparative investigation of radiation degradation of poly(1,4-butylene terephthalate), PBT; poly(ethylene terephthalate), PET; and poly(ethylene 2,6-naphthalene-dicarboxylate), PEN, was carried out. These polyesters were irradiated under vacuum at doses from 0.5 to 4 MGy. Data on solubility of the irradiated polyesters revealed absence of cross-linking. Molecular weights of PBT and PET decreased noticeably after irradiation, and radiation-chemical yields of destruction were quantified. NMR and UV spectra revealed changes in molecular structure upon irradiation of PBT. Efficiency and mechanism of radiation degradation of PBT, PET and PEN were discussed.