The relationship between exercise intensity, oxidative stress and antioxidant status has been studied in sixteen trained male athletes aged 20-25years. Subjects performed 30-40minutes of treadmill running at 65% of VO2 max(high intensity exercise). Blood samples were taken before and immediately after two exercise bouts for measurement of blood antioxidants, indices of lipid peroxidation and susceptibility of crythrocyte to peroxidation. Plasma concentrations of cholesterol(7.3%), vitamin C(7.5%) and uric acid(2.1%) were elevated a little after exercise at 65% of VO2 max(13.7%)were significantly high than before exercise(p<0.05). However, these exercise-induced changes could be partly due to significant decreases in plasma volume which occurred after both exercise bouts(p<0.05). Plasma volume decreased 5.85$pm$2.06% and 11.25$pm$2.87% with exercise at 65% and 85% of VO2 max, respectively. The erythrocyte susceptibility to peroxidation after exercise at 65% of VO2 max was unchanged compared with the value before exercise, whereas after exercise at 85% of VO2 max, it was significantly higher than after exercise at 65% and 85% of VO2 max as well as before exercise(p<0.05). A significant increase at 85% of VO2 max, it was significantly high than after exercise at 85% of VO2 max (29.10$pm$4.76ug/g Hb)when compared with the level before exercise (24.61$pm$3.45ug/g Hb)(p<0.05). The results suggest that exercise-induced changes in plasma levels of lipid peroxide and antioxidant need to be evaluated, taking the shift in plasma volume into consideration. Also, exercise at high intensity corresponding to 85% of VO2 max alters the erythrocyte antioxidant status in relation to exercise-induced of oxidative stress.