Cytokines at an inflammatory site may be a better indicator of the clinical severity of an infectious disease than the serum levels of the cytokines. Concentrations of interleukin-1β (IL-1β) in paired samples of cerebrospinal fluid (CSF) from 10 rabbits with experimental bacterial meningitis caused by H. influenzae type b, were measured, and compared to the concentrations of four cytokines; IL-1β, interleukin-6 (IL-6), Interleukin-8 (IL-8) and tumor necrosis factor-a (TNF-α) in CSF samples from 45 children with or without meningitis. The IL-1β concentrations in the CSF from rabbits with experimental meningitis were significantly higher than the concentrations in control animals without meningitis (p<0.001). The mean CSF concentrations of IL-8 from meningitic children were significantly higher than in the control group without meningitis (p<0.005). TNF-a was only detected in septic meningitis. Assays of IL-6, however, were not significantly different in the septic meningitis group, the aseptic meningitis group and the non-meningitis group. These data indicate a possible role of IL-1β, IL-8 and TNF-a as mediators in the meningeal inflammatory process in patients with meningitis and TNF-a, in particular, may play a role in the pathogenesis of septic meningitis.