We prospectively evaluated the inflammatory response to acute cerebral ischemia in 57 patients who were seen within 72 hours of ictus. All subjects had cerebrospinal fluid examination, complete blood count, sedimentation rate determination, and body temperature monitoring. Correlation analysis was done between these measurements and infarct volume, which was determined by computed tomography of the brain. We found a positive linear correlation between infarct size and the peripheral white blood cell count, specifically the polymorphonuclear leukocyte count. A relationship was also observed for the cerebrospinal fluid protein level, the gamma globulin level, and the cerebrospinal fluid/serum albumin ratio. The correlations observed presumably reflect the extent of tissue injury and secondary inflammatory response in acute cerebral ischemia.