The purpose of this study was (1) to demonstrate whether peripheral blood leukocytosis accompanies first afebrile seizures without bacterial infection, (2) to investigate the duration of leukocytosis, and (3) to assess the relationship between peripheral blood leukocytosis and seizure characteristics. Complete blood count was routinely obtained from all the patients. Blood and urine cultures were obtained from patients with leukocytosis. On the 24th hour of admission, a second complete blood count was obtained from patients with initial leukocytosis. Sixty-two children aged 4.0 +/- 3.6 years (range, 6 months-13 years)-31 boys (50%) and 31 girls (50%)--enrolled in the study. The findings showed that peripheral blood leukocytosis was found in 8% of afebrile children without status epilepticus and 41.6% of afebrile children with status epilepticus. An interesting finding of the study was that peripheral blood leukocytosis accompanied by afebrile seizures subsided in 24 hours. Transient leukocytosis could be found in children with afebrile seizures without bacterial infection.