Abstract: Objective To compare the role of procalcitonin（PCT） and blood culture in diagnosis of blood stream infection. Methods Data about patients with blood stream infection diagnosed with PCT and blood culture in our hospital from May 2008 to July 2009 were retrospectively analyzed.Blood was cultured in BacT/Alert 3D,a fully automatic consecutive detection system.Pathogens were identified using VETEKII,a fully automatic microorganism identifier.Semi-quantitative immunochromatography was used to detect PCT. Results The positive rate of PCT and blood culture was 23.8% and 22.9%,respectively.The sensitivity and specificity of PCT were 78.3% and 77.3%,respectively,with a positive and negative predictive value of 52% and 91.9%,respectively. Conclusion Semi-quantitative PCT has a certain sensitivity and specificity in diagnosis of blood stream infection,and is easy to perform and judge,and can thus be used in routine laboratory diagnosis of blood stream infection.