Twenty monkeys (macaccus rhesus) were examined by the following parameters: deformability of erythrocytes and mononuclear leukocytes, hemolytic activity of the serum, free hemoglobin of the serum and viscosity of plasma. The data obtained are accepted as standard because literature data on hemorrheology of monkeys are absent. Compared to relevant indices in humans, monkeys have increased hematocrit, serum hemolytic activity, erythrocytic rigidity index. Seven monkeys were used as the model of "donor" (6-8% blood loss). The above indices were measured before exfusion and on days 2, 7, 14 and 21 after exfusion. Maximal changes in rheology and hemolysis were observed on day 2 and 7 after blood loss which correlated with deviations of the red sprout of hemogeny.