Electron spin resonance (ESR) spectroscopy was employed for identification and quantification of the more stable free radicals generated by irradiation in bones of fish and beef. The samples were irradiated 1-5 kGy with gamma rays using Co-60 source. ESR spectroscopy was employed to detect irradiation in samples of fish and beef bones.  The results revealed that the irradiated samples showed strong asymmetric signals with g1 2.002 ± 0.001 and g2 1.998 ± 0.001 respectively, which was a clear indication of irradiation. The control samples were not irradiated and showed typical low intensity symmetric signals at g-value of 2.005 ± 0.001 revealing the absence of radiation treatment. It was also observed that intensities of signals due to hydroxyapatite radicals for 5 kGy were normally higher than 1 kGy radiation dose, showing the dose dependency.