Only male rats were used in the experimental studies of cerebrovascular disease to exclude any potential effects of hormones which may cause more inflammatory reaction in female rats. Inflammatory responses in cerebral infarctions may modulate acute tissue damage and repair to affect infarction size. The authors investigated the differences in the degree of cerebral infarction between both gender groups and the hypothesis that increased inflammatory responses in female rats may have adverse effect on cerebral infarction. 12-week-old Sprague-Dawley rats(10 males and 8 females) were subjected in this study. The right middle cerebral artery was ligated by a 10-0 nylon and both common carotid arteries were occluded by microclips for 30 minutes, and then the three vessels were opened to reperfuse. Their brains were obtained at 72 hours after the operations, and a focal cerebral infarction was established uniformly at right frontal lobe. The volume of the infarction was measured. Inflammatory cells were counted at the peri-infarct area. The mean volume of the cerebral infarction was 11.8+/-.9mm3 in the male group and 6.9+/-.1mm3 in the female group. The infarction volume was significantly larger in the male group(p<0.05). However the number of inflammatory cells, microglial cells, neutrophils, and lymphocytes in the peri-infarct area were not different significantly in the both gender groups(p>0.05). These data indicate that the infarction volume may be affected by gender but the cellular immunity was not influenced by gender and even have no direct effect on the cerebral infarction.