Cytokines play a role in meningeal inflammation and leukocyte recruitment. Research has demonstrated that levels of different cytokines are elevated in aseptic and viral meningitis. Unfortunately, previous data were confounded by the inclusion of multiple viral agents as a study group. The aims of the study were to determine the cerebrospinal fluid concentrations of various cytokines in an outbreak of a single viral agent and to correlate between cytokine levels and leukocytes. Cerebrospinal fluid samples, collected during an outbreak of echovirus type 4 meningitis in infants and children in Israel, were tested for routine characteristics. In addition, cytokine levels were measured in 71 meningitis patients and compared with those of 11 nonmeningitis patients. Concentrations of interleukin-6 (2417 +/- 2713 vs 28 +/- 20 pg/mL; P < 0.01) and interferon gamma (36 +/- 38 vs 4.8 +/- 0.9 pg/mL; P < 0.01) were significantly higher in patients with meningitis than in the control group, whereas soluble intercellular adhesion molecule-1 (1.12 +/- 2.6 vs 0.06 +/- 0.1 ng/mL) levels did not differ significantly. In addition, only interleukin-6 levels correlated with leukocyte counts in viral meningitis patients. Interleukin-6 was the most sensitive and specific characteristic in predicting meningitis in this homogeneous group of patients. Furthermore, only interleukin-6 correlated with leukocyte counts in the cerebrospinal fluid.