Abstract: Objective To investigate effect of hyperbaric oxygen (HBO) on neural stem cell proliferation in rats following ischemia-reperfusion injury.Methods SD rats were randomly divided into 3 groups:the sham surgery (SS) group,the ischemia-reperfusion (IR) group and the HBO treatment group.Middle cerebral artery occlusion (MCAO) was performed to develop the animal model.Reperfusion was made following 1.5-hour ischemia.Then,changes in the infarction area were observed respectively on day 4.11 and 31 with tri-phenyltetrazolium chloride (TTC) staining.After immunohistechemical staining,light microscopy was used to obtain numbers of 5-bromodeoxyuridine (BrdU) and nestin positive cells in cortex and striatum areas.Results TTC staining revealed that the infarction area of the HBO group at various time points was obviously smaller than that of the IR group.When compared with those of the SS group.numbers of BrdU and nestin positive cells in cortex and striatum all increased significantly in the IR group (P<0.05).And the numbers of BrdU and nestin positive cells increased markedly on day 11 and 31,following HBO therapy,when compared with those of the IR group (P<0.05).Conclusions HBO could effectively promote proliferation of neural stem cells in rats following ischemia-reperfusion injury.