Abstract: Genomic instability induced by radiation is characterized by the increased rate of acquisition of genetic alterations in the progenies of irradiated cell. These changes encompass a diverse set of biological end points, such as kary-otypic abnormolities, gene mutation and amplification, and delayed reproductive cell death etc. Damages of some key genes play important roles in the initiation and transition of genomic instability. Epigenetic factors may influence the onset of genomic instability. Loss of stability of the genome is one of the important aspects of radiation carcinogenesis.