Aim of the present study was to assess the increase of peripheral white blood cell (WBC) count and its clinical and prognostic significance in patients with cerebral ischemic infarction (CI). Thirty-six subjects (17 males, 19 females; mean age 73 +/- 10 years) with CI confirmed at CT scans were studied. A significant increase of WBC, not related to complicating infections, was observed in the early phase of CI. There was a significant linear correlation between the level of serum creatine phosphokinase and the number of circulating WBC which were higher in patients who died 6-30 days after the occurrence of CI. These data suggest that the increase in circulating WBC is dependent on the extent of the cerebral damage and should be considered as unfavourable prognostic sign