The hemorheological activity of a dry extract from Rhaponticum (Leuzea) carthamoides (Willd.) Iljin. was studied in spontaneously hypertensive rats (SHRs). A 14-day treatment of the test rats with a daily dose of 150 mg/kg improved the rheological characteristics, as manifested by a reduced viscosity of the whole blood and plasma, increased spontaneous erythrocyte aggregation and fibrinogen concentration, and increased erythrocyte deformability and electrophoretic mobility against the untreated control level.