This research was conducted for the purpose of studying the influence of exercise training on the level of SOD mRNA expression in human lymphocytes. 10 first-year high school boys (age 15-16), members of the high-school football club, were subjected to exercise training for a period of 3 months; using a bicycle ergometer before and after the exercise training, maximal exercise test was conducted. The subjects trained 2 hours a day, 6 days a week over the span of 3 months, as a regular part of their club activities. Blood samples were taken before and immediately after maximal exercise test before and after training, at rest and after training at the end of 1 month, 2 months and the end of the training period; expression of manganese-SOD (Mn-SOD) mRNA and copper-zinc SOD (Cu/Zn SOD) mRNA in their lymphocytes was measured. Results showed significant increases in both maximal oxygen uptake (VO₂max) and maximal voluntary ventilation (MVV), (p<0.001 and p<0.01, respectively), and the physiological effects of exercise training were verified. No significant changes were seen in expression of Mn-SOD and Cu/Zn-SOD mRNA at rest as a result of training. In maximal exercise tests, Cu/Zn-SOD mRNA expression levels showed no significant changes either before or after exercise training. Although Mn-SOD mRNA expression levels showed significant increases before exercise training in comparison to before maximal exercise test (p<0.05), significant changes after exercise training were not observed. From these results, the effects of exercise training on lymphocyte SOD mRNA were demonstrated to exert beneficial effects on Mn-SOD functions for an acute bout of exercise rather than on SOD mRNA expression at rest.