Abstract: Egr-1(early growth response-1)gene is an important member of the "Immediate Early Growth" gene family,participating in multiple radiation biological effects of the irradiated cells.Studies have shown that after ionizing radia-tion,Egr-1 gene can be activated at an early stage in many types of tumor and normal cells.Its actitivation and the conse-quent expression is believed to have a close relation to the change in cell growth,cell cycle and apoptosis of the irradiat-ed cells. Additionally,the radiation-inducible property of the Egr-1 gene regulating sequence confers potential clinical and genetic engineering uses.