Objective To investigate the relationship and mechanism between the serum level of high mobility group box protein-1(HMGB1)and the mortality rate in patients with sepsis.Methods The serum levels of HMGB1,superoxide dismutase(SOD)and malondialdehyde(MDA)in 48 patients with sepsis were determined.The clinical outcomes in those patients were recorded and anlyzed.Results After the onset of sepsis,the serum HMGB1 levels of both death group and survival group were increased gradually and peaked at 72h after the onset of the disease.The semm HMGB1 levels of death group were much higher than those of survival group except at 24h(t=6.07,6.20,24.43,all P＜0.05).The activity of serum SOD of death group was markedly lower than that of survival group at 12h,24h,48h and 72h(t=10.24,20.61,11.67,33.33,all P＜0.05),and the level of serum MDA of death group was significantly higher than those of survival group at all time points(t=26.06,22.17,23.86,9.49,5.95,all P＜0.05).There was a significantly positive correlation between the serum HMGB1 and MDA level.Conlusioa The increase in serum HMGB1 level may be the important reasoll for the increased mortality rate in patients with sepsis;Oxidant/antioxidant imbalance may be olle reason for the increase in serum HMGB1 level.