We have previously reported increased concentrations of interleukin (IL)-6 in CSF from patients with tonic-clonic seizures, where increased cytokine production most likely is a consequence of neuronal epileptic activity associated with seizures. The biological effects of IL-6 are mediated by other cytokines, which are studied here in addition to IL-6. The purpose of this study was to analyze levels of soluble cytokines from plasma and CSF from patients with newly developed tonic-clonic seizures. The concentrations of IL-6, IL-1 receptor antagonist (IL-1RA), IL-1 beta, tumor necrosis factor (TNF alpha) and nerve growth factor (NGF) were measured from plasma and CSF from 22 patients with newly developed tonic-clonic seizures within 24 h from the seizure and 18 controls. The mean concentrations of IL-6 were significantly increased in CSF (P < 0.001) and plasma (P < 0.01) after tonic-clonic seizures, there was some indication of increased concentrations of IL-IRA and no significant change in NGF, IL-1 beta or TNF alpha. Our study shows that cytokine network is activated in patients after recent tonic-clonic seizures. We provide evidence of intrathecal production of IL-6 associated with electrical seizure activity. (C) 2000 Elsevier Science B.V. All rights reserved.