Cerebrospinal fluid (CSF) examinations of 212 children aged two to 24 months with idiopathic nonfebrile seizures, complex febrile seizures, or status epilepticus, who had a lumbar puncture within 24 hours of the convulsion, were reviewed to determine whether an idiopathic convulsion can result in CSF abnormalities. Children with complex febrile seizures had a median CSF white blood cell count of 1 cell/mm3 (range 0-19 cells/mm3) and a median CSF polymorphonuclear (PMN) cell count of 0 cells/mm3 (range 0-8 cells/mm3). The CSF white blood cell (WBC) count was elevated above the upper limit of normal of 5 cells/mm3 in 9.8% and the absolute number of polymorphonuclear cells was more than 0 cells/mm3 in 26.2% of the complex febrile seizure subjects. Values at the 95th percentile were calculated; a total of 8 WBC/mm,3 4 PMN/mm,3 protein of 73 mg/dl and glucose of 119 mg/dl determined the 95th percentile CSF values for the patients with complex febrile seizures. Patients with nonfebrile seizures or with status epilepticus had similar findings. We conclude that complex febrile, idiopathic nonfebrile convulsions or status epilepticus may affect CSF findings in children: CSF with > 20 WBC/mm3 or > 10 PMN/mm3 should not be attributed to seizures.