A study of free radical processes (FRP) markers in 381 patients with ischemic and hemorrhagic stroke revealed the importance of oxidant stress that was most severe in patients with large volumes of stroke. Intensification of FRP consists in the reduction or inversion of oxygen FRP activity and increase in lipid free radical FRP that last till the patient discharge from a hospital. FRP indicators are early prognostic markers of stroke course and outcome. An inverse correlation between the level of anti peroxide plasma activity (APA) and the dynamics of the increase in stroke lesion from 1 to 20 days, and direct correlation between malondialdehyde (MDA) titer and the risk of hemorrhagic transformation and growth of the lesion from 5 to 20 days of disease were revealed. The results indicate that inclusion of antoixidant therapy should be conducted as early as possible after stroke using high doses of drugs in severe cases. The high efficacy of antioxidant cytoflavin in a daily dose of 20 ml in patients with stroke of different character and severity was shown. The positive effect of cytoflavin on FRP markers was accompanied by the improvement of clinical and morphological presentations and stroke outcome.