Physical exercise is considered protective against oxidative stress-related disorders. However, there is increasing evidence that strenuous activity may induce increased oxidative stress response. This study investigated the impact of vigorous physical activity on serum oxidative stress markers in 36 soccer and 12 basketball National League adolescent athletes 40 minutes before and 15 minutes after a National League game. Serum total peroxide, fibrinogen, polymorphonuclear (PMN) elastase, and myeloperoxidase levels were determined. No significant differences in any of the measured parameters were observed before the match. Soccer players exhibited significantly lower total peroxide (P < .05) and higher PMN elastase concentrations (P < .05) than that of the basketball athletes after the game. A number of important differences between these 2 sports, such as duration or total aerobic and anaerobic demands, may affect oxidative status. These parameters need to be further examined in order to elucidate the different effects of these 2 sports on postexercise oxidative status.