1171 The propolis of honeybee hives has long been used in folk medicine. Recent studies show propolis exhibits a broad spectrum of activities such as antibiotic, antiinflammatory, antifrugal, and antitumorigenic properties. Along with these activities, antioxidative effects of propolis and its components have also been studied in vitro. PURPOSE: To investigate the effect of propolis supplementation on antioxidative system to oxidative stress induced by maximal graded aerobic exercise. METHODS: In this study, a randomized double-blind design were used. In the experimental group, 17 subjects (38.4 ± 10.1yrs) took soft capsule type propolis (800mg/day, Bid) for 2 weeks. In the control group, 17 subjects (n = 17, 38.4 ± 10.1 yrs) received the placebo. 5ml blood samples were taken by intravenous during the resting state, 1min after maximal treadmill exercise (bruce protocol) and 30min later. after recovery. We examined the concentration of plasma malondialdehyde (MDA), the percentage of DPPH degradation, and acitivities of superoxide dismutase (SOD). RESULTS: In the propolis group, the MDA levels had decreased at resting level after treatment (3.22 ± 1.58 vs. 2.76 ± 1.91nmol/dl) compared to the control group (3.98 ± 2.28 vs. 4.26 ± 2.24nmol/ml, P<0.05). The rate of decrease was also higher 1min (12% vs, −13%, P<0.05) and 30min (17% vs, −25%, p<0.05) after exercise in the propolis group, even though there was no significant differences between the groups. There was no marked significant difference in the percentage of DPPH degradation between the groups, but in the control group, there was significant differences between pre and post values 30min upon completion of exercise (20.92 ± 4.16 vs, 16.92 ± 7.36%, p<0.05). It means that the propolis could retard the degradation rate of the scavenging activities of the DPPH. There were a lot of variation in the SOD level during our study. So we could not detect the trend. CONCLUSIONS: We found that Propolis could help the antioxidant system at postexercise specially MDA level and the scavenging activities of the DPPH. But we couldn't determine the SOD level. Therefore, further study should be continued to evaluate our results