We carried out the retrospective analysis of 300 disease histories of patients with stroke hospitalized in the first 24 h of the disease. The presence of leukocytosis and its severity were evaluated as predictors of outcome. The level of leukocyte-erythrocyte aggregations in the blood film was determined in some patients. The analysis revealed that the higher was leukocytosis, the more severe was the course of stroke and the higher was frequency of fatal outcomes. Patients with stroke more often had neutrophilic leukocytosis than monocytosis, the former was the predictor of worse prognosis. The most unfavorable prognosis was observed in patients with hemorrhagic stroke and leukocytosis. The higher was the number of leukocytes, the higher was the probability of fatal outcome in the first month of stroke. The level of leukocyte-erythrocyte aggregations dramatically increased in the blood of stroke patients that promoted the disturbance of microcirculation and worsened significantly the disease prognosis.