The purpose of this study was to examine effects of treadmill running training on superoxide product of spontaneously hypertensive rats. 20 males aged five week old rats were used for the experiments. They were randomly selected into experimental group (10 rats) and control group (10 rats) after being housed in laboratory for two weeks. The rats of experimental group performed treadmill exercise from 15 minutes for the first time to 35 minutes for the last one in order to familiar with experimental protocol (VO2max65~70%, 0.9km/h, 5 times/week, 35 minutes/session). They began to perform treadmill running at the age of eight weeks for eight weeks. Superoxide production and NADPH oxidase activities were measured on the aortal from end of experiment. All statistical analyses and description methods were computed by SPSS Version 10.0. Differences in the values between experimental group and control group were calculated using t-tests. The results of this study were: there wewe no significant differences in superoxide production, NADPH oxidase-drivened superoxide activity, NADPH oxidase activity between two groups (p>.05). Spontaneously hypertensive rats of experimental group were characterized by higher superoxide production and lower NADPH oxidase-drivened superoxide activity and NADPH oxidase activity in comparison with the control group. One possible explanation of this finding was that NADPH oxidase activity of experimental group was lower than the control group. It can be concluded that treadmill running for eight weeks was associated positively with superoxide product of spontaneously hypertensive rats.