Abstract: Objective To evaluate the role of combined quantitative procalcitonin（PCT） and blood culture in diagnosis of blood stream infection. Methods PCT and blood culture data about patients admitted to our hospital from June 2009 to April 2010 were retrospectively analyzed.Blood samples were cultured with the automatic BacT/Alert 3D system.Pathogenic bacteria were identified using the VITEK II system.PCT was assayed using the mini-VIDAS.B.RA..H.MS PCT.Data were analyzed using the SPSS17.0 statistical software. Results The positive rate of PCT and blood culture was 43.9% and 20.6%,respectively.The sensitivity and specificity of PCT were 87.5% and 67.4%,respectively,when 0.70 was taken as a cut-off value.The positive and negative predictive value for PCT was 41.0% and 95.4%,respectively. Conclusion Quantitative PCT can be used in diagnosis of blood stream infection with a rather good sensitivity and specificity by continuously monitoring infection in patients,and provide evidence for clinical decision-making.