Neutrophils accumulate initially in the cerebrospinal fluid (CSF) of aseptic meningitis, perhaps because of increased levels of granulocyte colony-stimulating factor (G-CSF), macrophage inflammatory protein-1alpha (MIP-1alpha), and IL-8 in the subarachnoid space. We studied levels of these cytokines in children with aseptic meningitis using ELISA. When meningeal symptoms existed, IL-8 levels (1399 +/- 1600 ng/l, n = 32) in the CSF were significantly higher than those either after meningeal symptoms disappeared (61 +/- 56 ng/l, n = 18) or in controls (44 +/- 63 ng/l, n = 27) (P < 0.0001). High levels of IL-8 on admission dropped sequentially. Significant correlations were found between IL-8 levels and either neutrophil counts (r = 0.612), G-CSF levels (r = 0.873) or MIP-1alpha levels (r = 0.623) in the CSF of the affected patients (P < 0.0001). IL-8 values in serum were lower than in the corresponding CSF samples from all individuals with meningeal symptoms. The IL-8 mRNA was detectable by reverse-transcribed polymerase chain reaction (PCR)-assisted amplification in fresh leucocytes from the CSF, but not from the peripheral blood of a healthy volunteer. The culture of CSF mononuclear cells produced high levels of IL-8 (approximately 2750 ng/l). These data indicate that IL-8 levels rise transiently at the initial stage of aseptic meningitis, and that mononuclear cells that migrate into the CSF are a cellular source of this chemokine. We suppose that IL-8, in addition to G-CSF and MIP-1alpha, contribute to the localized neutrophil accumulation during the disease.