Recent advances have been made in the understanding of molecular events following cellular exposure to ionizing radiations, suggesting that new molecular targets could be used to modulate radio-induced cellular response, including genes and their encoded protein involved in DNA repair, signal transduction, apoptosis and cell cycle regulation. These potential molecular targets include some radio-induced cytokines and growth factors that could modulate radiation response in irradiated normal tissues (TGF beta). In addition, in order to increase tumor cell lethality after irradiation exposure, two promising approaches have been recently explored, including firstly the modulation of radiation-induced apoptosis via the transfer of genes involved in the regulation of apoptosis (p53), and secondly the modulation of double strand break DNA repair.