The radioprotecive effects of a major component of green tea polyphenone,(—)epigallocatechin gallate (EGCG) was examined by using the radiation — induced cell death model in Human — derived liver L02 cells,with the methods of MTT and pulsed field gel electrophoresis (PFGE). EGCG substantially suppressed the radiation — induced mortality under treatment concentration of 5—50μmol/L, where the cytotoxicity was mild. Significant suppression of DNA double strand break (DSB) was also observed with treatment of cells with 50μmol/L of EGCG. Both treatment prior to and behind irradiation was effective. It could be suggested that EGCG could either scavenge OH• or repair the damage of DNA of L02cells effectively.