Abstract: Objective To study the level of Th17 cells in peripheral blood of patients with sepsis and its significance. Methods Fiftyfive patients admitted to Emergency Department and Surgery ICU of our hospital in March-July 2009 were divided into sepsis group（n=18）,severe sepsis group（n=29）,and septic shock group（n=8）.Expression of Th17 cells in CD4+ T cells was detected by flow cytometry.Thirty healthy individuals served as controls. Results The expression rate of Th17 cells was 2.41%±0.62%,3.36%±1.42%,5.33%±2.67%,and 2.1%±0.89%,respectively,in control,sepsis,severe sepsis,and septic shock groups.The expression rate of Th17 cells was the highest in severe sepsis group with no significant difference between septic shock and control groups. Conclusion The expression of Th17 cells is increased in sepsis patients,suggesting that Th17 cells may play an important role in pathogenesis of sepsis.