Objective:To identify the sensitivity,reliability in diagnosis and prediction the outcome for neonatal sepsis and septic shock.Methods:Plasma PCT levels of 108 neonates with sepsis(40 with septic shock) were measured by semi-quantitative solid phase immunoassay.At the same time,the plasma CRP and IL-6 levels were observed.Results:The positive rate of PCT was significantly higher in patients with neonatal sepsis and septic shock compared with control group and plasma PCT levels of septic shock group was the highest.The prevalence and fatality rate of septic shock were associated to the plasma levels of PCT,the higher was the PCT,the much higher was the prevalence and fatality rate of septic shock.The plasma PCT levels were significantly correlated with the plasma levels of CRP and IL-6.The sensitivity(87.5%),specificity(82.4%),positive predictive values(74.5%),accuracy(84.3%) of PCT all higher than that of CRP and IL-6.Conclusion:Increased plasma PCT levels in the early stage of neonatal sepsis and septic shock were associated with the severity of illness.PCT is superior than CRP and IL-6 as a marker of severe bacterial infection.