Purpose: Hypoxia is known to cause brain damage. However, we think there may be the difference of the effect on the brain according to the degree of hypoxia. The aim of this study is to investigate the potential effect of mild hypoxia. Methods: We used hippocampal tissue cultures at 7 and 14 days in vitro (DIV) from SD rats aged 7 days. The tissue cultures were exposed to 10% oxygen for 60 minutes. 24 hours after this hypoxic insult, propidium iodide fluorescent images were obtained. Damaged areas in CA1, CA3, and DG were measured using an image analysis software. We estimated the extent of damage 24 hours after hypoxic exposure. Hypoxia exposed tissues were compared to tissues not exposed to hypoxia. The ratio of damaged area at 24 hours to the total damaged area after NMDA treatment was calculated. Results: In the 7 DIV group, compared to control tissues, hypoxia-exposed tissues tended to have decreased damage in two regions(CA1, DG), but this decrease was not statistically significant. In the 14 DIV group, compared to control tissues, hypoxia-exposed tissues showed decreased damage; this decrease was not significant in the CA3 and, DG, but it was significant in the CA1. Conclusion: Most tissues showed a tendency to have less damage after hypoxic exposure. Therefore, we think that mild hypoxia might have a protective effect in the brain.