We studied 203 patients (116 male, 87 female, mean age 34,6±8,2 years) with ischemic stroke (IS). The study was carried out in one week - 14 months after the development of stroke. All patients underwent MRT/CT of the brain, cerebral angiography (MRA, rarely - CTA or conventional angiography), duplex ultrasound and echocardiography. Antiphospholipid antibodies, homocysteine, platelet aggregation, blood clotting, methylenetetrahydrofolate reductase, prothrombin and factor V Leiden gene mutations were also studied along with routine clinical and biochemical blood tests. When it was indicated, antinuclear antibodies, DNA antibodies, antibodies to some viruses were studied and muscle biopsy was performed. The causes of IS were as follows: cerebral artery dissections (25%), cardioembolism (12%), antiphospholipid syndrome (11%), coagulography (7%), arterial hypertension (8%), atherosclerosis (3%), mitochondrial cytopathy (3%), cerebral vasculitis (1%), Moya-moya disease (0,5%), cerebral artery spasm after the aneurysm disruption (0,5%). The cause of IS remained unknown (cryptogenic stroke) in 29%. In a half of these cases, clinical presentations suggest the cerebral artery dissection as a cause of IS. However in the acute period the diagnosis was not verified by angiography which was conducted only in the late stage of stroke (3 months or more after stroke development).