Background: Spindle trees (Euonymus japonica Thunb.) growing in an industrial complex area containing pollutants is chronically injured thus need to build up their resistance. Antioxidant enzymes and cell membrane stability have been widely used to differentiate stress tolerance. Materials and Methods: Leaves of spindle trees from a clean control area (Kijang) and an industrial area (Onsan) where is one of the heavily polluted areas in Korea were subsequently irradiated with 0, 50 and 100 Gy of gamma rays from a 60Co isotopic source, and evaluated for the level of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) and lipid peroxidation (LPO). Results: Air pollution-stressed plants showed better adaptation to ionizing radiation (IR) stress and are better protected from the oxidative damage, and rapidly up-regulate their antioxidative systems. The adaptive plants growing in the polluted area are less sensitive to consecutive oxidative stresses such as gamma rays, having a higher capacity of resistance to ionizing radiation, compared to the samples taken from the clean area. Conclusion: Air pollution-stressed plants showed lesser changes in the level of antioxidant enzymes after irradiation due to their enhanced antioxidant capacity. The enzymatic differences in plants irradiated with gamma rays can be used as biochemical end-points for environmental monitoring.