Cerebrospinal fluid levels of tumor necrosis factor-alpha and interleukin-1 beta in 78 children with nonbacterial, bacterial and tuberculous meningitis, and in 34 control subjects were analyzed in order to evaluate the involvement of these cytokines in the pathogenesis of acute bacterial meningitis and their discriminative value between different etiologies of meningitis. Tumor necrosis factor-alpha and interleukin-1 beta levels were significantly higher in bacterial and tuberculous meningitis than in aseptic meningitis and in control subjects (p < 0.0001). There was no difference in the levels of tumor necrosis factor-alpha and interleukin-1 beta between nonbacterial meningitis and control groups. The finding that both tumor necrosis factor-alpha and interleukin-1 beta are increased in the cerebrospinal fluid of patients with bacterial and tuberculous meningitis whereas normal levels of these two cytokines have been found in patients with nonbacterial meningitis signifies that these cytokines may be used to differentiate between bacterial and nonbacterial meningitis.