Stress will induce various changes in human metabolism. The remarkable phenomenon of these changes is increased energy metabolism that can induce many reactive oxygen species (ROS) production. ROS can peroxidize cellular macromolecules including lipid and protein. The object of this study was to investigate that stress may induce cellular damage by producing ROS and that Rooibos tea can protect cells against reactive oxygen species by immobilization stress in SD rat. The stress group significantly increased in 5-hydroxyindole acetic acid (5-HIAA), one of the stress hormone. Rooibos tea treatment had no effects on 5-HIAA contents, but body weight of Rooibos tea treated rat more increased than that of only the stress group. It was suggested that Rooibos tea colud not affect stress response itself, but protect against the another mechanism. We thought that the oxidative damage was caused by increased energy metabolism. Protein degradation level and lipid peroxide formation on index of oxidative damage significantly increased in the stress group. But the stress-induced activity change could not be observed in antioxidative enzymes such as superoxide dismutase, glutathione peroxidase and glutathione reductase. But the catalase activity of the brain significantly was inhibited by the stress. From these results, it was suggested that the immobilization stress induce the brain oxidative damage. However the oxidative damage was inhibited by feeding Rooibos tea containing various antioxidants, such as polyphenol, flavonoid and so on. Therefore, Rooibos tea have the protective effects against the stress caused by the ROS mediated cellular damage.