Abstract： Objective To evaluate the effect of hyperbaric oxygen (HBO) treatment on the expression of nestin in a model of right middle cerebral artery occlusion (MCAO) in rabbits. Methods Seventy healthy rabbits were dividod into 3 groups: the rabbits in MCAO+HBO group(n=30) were treated with HBO immediately after MCAO, once a day, consecutively for 20 d; the rabbits in MCAO group (n=30) were not trcated with any therapy after MCAO; the control group (n=10) received the same operation as that of MCAO group except MCAO. Rabbit behaviors and volumes of infarction were observed, and the expression of nestin was measured by immunocytochernistry 10 and 20 d after MCAO. Results Behaviors' scores and volumes of infarction were better in MCAO+HBO group than the MCAO group (P<0.05). 10 d after MCAO, the number of nestin-immunoreactive cells of MCAO+HBO group and MCAO group was respectively 15.88±1.2 and 6.63±1.6; 20 d after MCAO, the number in MCAO+HBO group and MCAO group was respectively 20.03±1.6 and 6.82±0.8. The number of nestin-immunoreactive cells in MCAO+HBO group was significantly higher compared with that of MCAO group (P<0.05). Conclusion Early applications of HBO and repeated administration of HBO for 20 d can evidently improve the behaviors and infarct size and elevate the expression of nestin in rabbit models of MCAO.