Exercise generates free radicals only when it is exhaustive. Free radicals are involved in tissue damage caused by exercise. Antioxidant vitamins (vitamin C and E) and other antioxidants such as coenzyme Q, and N-acetyl cysteine prevent muscle damage and decrease muscle fatigue. The main aim of this paper was to test the possible protective effect of two new antioxidants, cyanoside chloride and chromocarbe diethylamine, on the oxidative stress generated by exhaustive exercise. The antioxidants were given to rats daily (50 mg/kg) in drinking water for 30 days. Blood oxidized glutathione/ reduced glutathione ratio, and plasma malondialdehyde levels were determined as indexes of oxidative stress. Plasma creatine kinase, alanine-aminotransferase and lactate dehydrogenase activities were used as markers of muscle damage. Both cyanoside chloride and chromocarbe diethylamine were more effective than vitamin C in the prevention of glutathione oxidation in blood. Furthermore, cyanoside chloride and chromocarbe diethylamine partially prevented muscle damage. Chromocarbe diethylamine was the most effective compound in the prevention of exercise-induced lipid peroxidation (malondialdehyde) in plasma.