PURPOSE: To avoid a unnecessary lumbar puncture, we tried to find a useful tool for prediction of meningitis in infants. METHODS: One hundred and twenty four patients underwent a lumbar puncture at Chungbuk National University Hospital from Jan 1, 2011 to Dec 31, 2011. We divided them into 2 groups by the evidence of meningitis, and compared laboratory findings and clinical manifestations. RESULTS: There were 30 patients for meningitis group and 94 patients for control group. Meningitis group revealed lower serum monocyte percentage (meningitis group 10.1+/-4.7%, control group 12.2+/-5.0%, P=0.049) than control group. Other laboratory findings and clinical manifestations showed no statistically significant differences between two groups. CONCLUSION: Serum monocyte percentage could help to predict meningitis in young infants, but it is not enough to replace a lumbar puncture. We therefore think that it requires a more accurate non-invasive diagnostic tool to detect meningitis.