Radiation induced markers were investigated for the detection of irradiated oranges imported from America. In the DNA comet assay, the non-irradiated and irradiated samples showed the comets with long tails in both seed and flesh. Though this tendency was maintained for 6 weeks, identification of non-irradiated or irradiated samples was impossible. In the thermoluminescence (TL) measurement, the non-irradiated samples revealed a glow curve with low intensity at about 28$0^{circ}C$, while the irradiated samples showed with higher intensity at around 18$0^{circ}C$. There were no remarkable changes in detection properties for 6 weeks after irradiation. The TL ratio of area for TL$_1$ glow curve to TL$_2$ was below 0.1 for the non-irradiated samples and 0.5 or more for the irradiated ones during storage. In the electron spin resonance (RSR) measurement, irradiated oranges showed an unspecific central signal in all parts (seed, flesh and peel), so the detection for radiation treatment of oranges was impossible. Based on the results, DNA comet assay and ESR were not useful for the detection, but TL was appropriate to search radiation induced markers of oranges during storage period. The detectable period during storage is confirmed by sensory evaluation.