Objectives To investigate the changes of erythropoietin(EPO)expression in rats after focal cerebral ischemia/reperfusion injury.Methods Male Sprague-Dawley rats were randomly divided into normal,sham,cerebral ischemic/reperfusion(CIR)groups.Middle cerebral artery occlusion(MACO)model was established by Longa's method,and reperfusion was followed 2 hours after occlusion in CIR group.The rats' brain neurological deficit scores were evaluated at 24 h,48 h,72 h and 96 h after reperfusion.The protein expression of EPO was determined by immunohistochemistry staining and Western blotting in each time points.Results The rats' brain neurological deficit scores at 48 h,72 h and 96 h were significantly increased(3.40±0.32,3.60±0.17,3.70±0.21,all P<0.05)compared with those at 24 h(3.00±0.22)after reperfusion in CIR group.The results of immunohistochemistry staining and Western blotting showed that the positive expression of EPO proteins in rats started at 24 h(0.36±0.05,140.20±0.30)after cerebral ischemic/reperfusion injury,increased significantly at 48 h(1.09±0.10,145.40±0.16),reached the peak at 72 h(1.29±0.09,156.23±0.12),began to decline at 96 h(0.98±0.04,141.56±0.36).Conclusions Cerebral ischemia and reperfusion injury can induce increased expression of EPO protein,which suggests that EPO may have protective effect on nerve cells under the condition of ischemia and reperfusion.