Abstract：The purpose of this study was to investigate the exhaustive exercise-induced oxidative stress and the protective effect of oolong tea supplementation on malondialdehyde (MDA) levels, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in rat gastrocnemius muscle. Thirty-two male Sprague-Dawley rats were randomly divided into the following four groups: 1. control (C, n=8), 2. exhaustive exercise (CE, n=8), 3. oolong tea (O, n=8), 4. oolong tea-exhaustive exercise (OE, n=8). The amount of oolong tea extract supplementation was 0.5g/kg bodyweight per day for 4 weeks. The exhaustive exercise started at 10% grade, 15m min^(-1) for 10 min followed by gradual increases of treadmill speed and times until exhaustion. Two-way ANOVA was performed to examine the effects of exhaustive exercise and oolong tea supplementation on MDA, SOD, and GPx activities. The results showed that exercise-induced MDA levels were significantly higher than non-exercised rats (p＜.05), while MDA in OE group were significant lower than CE group (p＜.05). Muscle SOD activities in exercised rats were higher than non-exercised rats (p＜.05). Oolong tea supplemented rats also have higher SOD activities than non-oolong tea supplemented rats (p＜.05). Moreover, GPx activities in exhaustive exercised rats were significantly higher than non-exercised rats (p＜.05), while GPx activities in oolong tea supplemented rats were significantly higher than non-oolong tea supplemented rats (p＜.05). It is concluded that exhaustive exercise could result in oxidative stress. However, oolong tea supplementation is beneficial to decrease oxidative stress and increase the antioxidant status. (Full text)