The antioxidant effect of an adenosine A1 receptor agonist cyclopentyladenosine was studied on the model of focal cerebral ischemia. Ischemic injury of the brain was accompanied by changes in LPO processes (in the blood and brain tissue) and failure of some factors for antioxidant protection (peroxidase and catalase) that inactivate reactive metabolites. Changes in the ratio between LPO and antioxidant protection were less pronounced after treatment with cyclopentyladenosine.