ABSTRACT The aim of the present study is comparison of changes of principal hemorheological factors responsible for blood flow disorders in the microcirculation in patients with ischemic brain infarcts. It was found that in venous blood samples the erythrocyte aggregability (examined with a direct, highly sensitive, quantitative technique) was considerably more increased (by mean of 120%) than the blood plasma fibrinogen contents, blood plasma viscosity, and hematocrit which increased only by 23.7%, 7.4% and 3.6%, respectively, as compared to the same hemorheological factors in the healthy controls.