Abstract： Objective To investigate the changes of circulaling progenitor cells and endothelial progenitor cells(EPCs)in non-septic and septic shock patients using flow cytometry.Method A total of 27 sepsis patients hospitalized in emergency department of Zhongshan hospital during August 2007 to February 2008 were enrolled in this study.The patients were dividedinto septic shock group(n=12)and non-septic shock group(n=15).Ten healthy individuals and ten non-sepsis ICU patients were collected as controls.Peripheral blood mononuclear cells(PBMCs) were isolated by Ficoll density gradient centrifugation,and EPCs labelled with antibodies against CDl33,CD34 and VEGFR-2 were identified and isolated by three-color fluorescence flow cytometry.Differences within the groups were analyzed using One way ANOVA.Results The percentages ofprogenitor cells and EPCs in the PBMC fraction in healthy controls were(0.25%4-0.14%),(0.09%-I-0.02%),respectively,and those in ICU controls were(O.38%.4-0.29%),(0.12%.4-0.02%).The percentages of progenitor cells and EPCs were significantly higher in栅sel如c shock patients(0.57%±0.12%),(0.22%.4-0.10%)than in heathy and non-sepsis ICU controls(P<0.05).However.the percentages of progenitor cells and EPC8 in septic shock pa.tienta(O.20%±0.12%,0.04%-t-O.01%)was obviousely lower than those in healthy,ICU controls and ilionseptic shock patients(P<0.05).Sptic shock survivors had significantly higher numbers of cEPCs than nonsur.vivors(P<0.05).Conclusions The level of progenitor cells and EPC8 in peipheral blood of sepsis patients might be the valuable markers to as.se88 the severity and outcome ofthese ptienS.