It is well established that the radio-sensitivity is dependent of cell cycle progression, and among the each stage of interphase, G2 phase is the most radiosensitive, G1 phase is the second radiosensitive, S phase is the last radiosensitive, while Go phase is radio-resistent for absent oxygen and enough repairing time. Previous studies led to the conclusion that G2 phase is a very important stage. There are two techniques to study the chromosome aberrations in G2-cells, namely, G2-assay and G2-PCC technique. The G2-assay is to analyze the subsequent metaphases after irradiation, and with which studies indicate that cells It is well established that the radio-sensitivity is dependent on cell cycle progression, and among the respective stages of interphase, G2 phase is the most radiosensitive, G1 phase is the second radiosensitive, S phase is the last radiosensitive, while Go phase is radio There are two techniques to study the chromosome aberrations in G2-cells, namely, G2-assay and G2-PCC technique. The G2-assay is to analyze the subsequent metaphases after irradiation, and with which studies indicate that cells