The aim of this study was to assess the effects of eight weeks of continuous running trainingand four weeks of detraining on lipid peroxidation (MDA) and anti-oxidative system response after an acute exercise session. For this purpose, 20 sedentary healthy males were randomly divided into two groups: experimental and control. At the beginning, before and after one acute exercise session, blood samples were taken to evaluate lipid peroxidation (MDA), uric acid, bilirubin and total protein. Then, the experimental group was trained by continuous running three sessions per week for eight weeks while control group did not participate in any exercises during this period. After eight weeks, blood samples were taken again before and after an acute exercise session in order to measure the variables. After four weeks of detraining following eight weeks of exercise, experimental group participated in the third acute exercise session and blood samples were similarly taken in order to measure the variables. The results of one-way ANOVA with repeated measures indicated that lipid peroxidation (MDA) and uric acid significantly increased after one acute exercise session in the experimental group after eight weeks of exercise (P<0.05). But, No significant differences were observed in bilirubin concentration and total protein after eight weeks of exercise (P>0.05). Although significant increases were observed in lipid peroxidation (MDA) after four weeks of detraining (P<0.05), the changes in uric acid concentration, bilirubin and plasma total protein were not significant (P>0.05). It can be concluded that eight weeks of continuous running training may create adaptation in anti-oxidative system and oxidative stress, but the effects of oxidative stress is reversed due to detraining.