GST-TAT-SOD　was　the　fusion　of　superoxide　dismutase　(SOD),　cell-permeable　peptide　TAT,　and　glutathione-S-transferase　(GST).　It　was　proved　to　be　a　potential　selective　radioprotector　in　vitro　in　our　previous　work.　This　study　evaluated　the　in　vivo　radioprotective　activity　of　GST-TAT-SOD　against　whole-body　irradiation.　We　demonstrated　that　intraperitoneal　injection　of　0.5　ml　GST-TAT-SOD　(2　kU/ml)　2　h　before　the　6　Gy　whole-body　irradiation　in　mice　almost　completely　prevented　the　splenic　damage.　It　could　significantly　enhance　the　splenic　antioxidant　activity　which　kept　the　number　of　splenic　white　pulp　and　consequently　resisted　the　shrinkage　of　the　spleen.　Moreover,　the　thymus　index,　hepatic　antioxidant　activity,　and　white　blood　cell　(WBC)　count　of　peripheral　blood　in　irradiated　mice　pretreated　with　GST-TAT-SOD　also　remarkably　increased.　Although　the　treated　and　untreated　irradiated　mice　showed　no　significant　difference　in　the　growth　rate　of　animal　body　weight　at　7　days　postirradiation,　the　highest　growth　rate　of　body　weight　was　observed　in　the　GST-TAT-SOD-pretreated　group.　Furthermore,　GST-TAT-SOD　pretreatment　increased　resistance　against　8　Gy　whole-body　irradiation　and　enhanced　30　d　survival.　The　overall　effect　of　GST-TAT-SOD　seemed　to　be　a　bit　more　powerful　than　that　of　amifostine.　In　conclusion,　GST-TAT-SOD　would　be　a　safe　and　potentially　promising　radioprotector.