OBJECTIVE: To detect the levels of interleukin8 (IL-8) and tumor necrosis factor (TNF) in the cerebrospinal fluid (CSF) in children with purulent meningitis (PM) and viral encephalitis(VE). METHODS: Levels of IL-8 and TNF in CSF were determined using ELISA in 20 children with (PM), 17 children with viral meningoencephalitis (VME), 25 children with (VE), and 15 normal children who served as the controls. RESULTS: The levels of CSF IL-8 and TNF in the PM group ［(443±247) ng/L and (640±283) ng/L］ were significantly higher than those in the VME group ［(184±86) ng/L and (154±95) ng/L］, VE group ［(54±36) ng/L and (30±26) ng/L］ and control group ［(27±20) ng/L and (24±21) ng/L］(P<0.01). The levels of CSF IL-8 and TNF in the VME group were also significantly higher than those in the VE group and control group (P<0.01). CSF IL-8 levels in the VE group were higher than those in the control group (P<0.05), but there was no significant elevation in CSF TNF concentrations. A significantly positive correlation was found between IL-8 and TNF in the PM and VME groups (r=0.682, P<0.01 and r=0.534, P<0.05, respectively). CSF IL-8 levels were significantly related to neutrophil counts in patients with PM (r=0.777, P<0.01), but no significant relationship was shown between CSF IL-8 levels and neutrophil counts in children with VME and VE. There was no correlation between CSF TNF concentrations and neutrophil counts in the three patient groups. Nor was there any correlation between CSF IL-8 and TNF levels and other inflammatory parameters including CSF mononuclear cell counts, and protein and sugar levels in the three patient groups. CONCLUSIONS: IL-8 and TNF are important mediators in the meningeal inflammatory process in children with meningitis. The determination of IL-8 and TNF levels may be valuable in the diagnosis of purulent meningitis.