This study is aimed to investigate the effect of exercise on oxidative stress in hemodialysis patients. Eighteen subjects will be selected from patients undergoing chronic hemodialysis three times a week in a treatment center. The patients must have no limit for and being interested in doing exercise. They will be enrolled in an exercise program that will be performed during each hemodialysis session for eight weeks. Meanwhile, 18 patients undergoing hemodialysis with the same condition will be selected as the control group. The exercise will be cycling with a minibike during the first hour of dialysis. The exercise will last 20-30 minutes, with a maximum time of 45 minutes, depending on patient’s endurance. Before the begining of hemodialysis session and exercise, blood samples will be taken from the patients in each group and will be stored for later evaluation on inflammatory markers, including albumin, C-reactive protein (CRP), white blood cells, and serum ferritin. Other parameters such as nitrosative stress factors and the end products of lipid peroxidation such as malondialdehyde will be also examined. In addition, total plasma antioxidant capacity such as ferric ion reducing capacity, and thiol group including glutathione will be assessed. After eight weeks exercise, all the mentioned parameters will be measured again in both groups. Finally, the results of the tests before and after the eight weeks will be compared between groups.