An electron-beam (EB) irradiation/catalytic oxidation system was developed for the purification of a volatile organic compound (VOC) gas stream under a practical gas flow condition. This system consists of a compact-sized electron accelerator and an ozone decomposition catalyst, which is MnO2. The removal of toluene and/or xylene and their mineralization were examined with and without catalytic oxidation for a gas stream at a flow rate of 500 (N)m(3) h(-1). A combined catalyst bed enhanced the removal of VOCs and the mineralization of VOC and its irradiation organic byproducts. For example, for an initial concentration of 5 ppmv, the removal ratio of toluene and xylene increased from 60% to 91% and from 81% to 91%, respectively, at a dose of 4.4 kGy. The mineralization ratio increased from 42% to 100% by the catalytic treatment at doses higher than 9.3 kGy. Furthermore, the yield of CO2 to COx increased from 52-60% to 83-89% by the catalytic treatment.