Objective: To determine the diagnostic value of serum white blood cell (WBC) count, fever (>38˚C) and WBC rise (>10%) for bacterial meningitis in patients with severe traumatic brain injury (TBI).Method: This cross-sectional study was conducted in Shahid Rajaei hospital affiliated with Shiraz University of Medical Sciences during a 1-year period from 2013 to 2014. We included consecutively all the patients with severe TBI admitted to our center during the study period who were febrile (>38˚C orally) and underwent lumbar puncture (LP) and analysis and culture of cerebrospinal fluid (CSF). Laboratory analysis of CSF and blood were performed within 2 hours of LP. CSF culture was considered the gold standard for diagnosis of bacterial meningitis. The sensitivity, specificity, positive and negative predictive value (PPV, NPV) of peripheral blood WBC count, fever (>38˚C) and WBC rise (>10%) was determined according to the CSF culture.Results: Overall we included242 consecutive patients with severe TBI. The mean age of the participants was 32.8 ± 17.4 years. Acinetobacter was the most common organism found in the CSF cultures. The sensitivity and specificity of peripheral WBC count (>10,000)was 48.4% (95% CI: 0.42-0.56) and 47% (95% CI: 0.37-0.58) respectively. The PPV and NPV was 13.1% (95% CI: 0.33-0.52) and 84.8% (95% CI: 0.42-0.61), respectively. The AUC for WBC count was 0.478 (95% CI: 0.37-0.58) indicating low accuracy for the diagnosis of bacterial meningitis. The AUC for WBC rise (>10%) and temperature >38˚C was0.460 (95% CI: 0.351-0.569) and 0.517 (95% CI: 0.410-0.624) respectively, both indicating low accuracy for diagnosis of bacterial meningitis. Conclusion: The results of the current study indicates that peripheral blood leukocyte count, fever (>38˚C) and WBC rise (>10%) is a non-reliable marker for diagnosis of bacterial meningitis in patients with severe TBI.