Effects of 50% ethanolic extract (JR-ext) from Chinese Rehmanniae Radix (the steamed and dried root of Rehmannia glutinosa, "Jyuku-Jio"in Japanese) on the hemorheology of inflammatory, thrombosic and intact animals were examined in the in vivo models. JR-ext (200 mg/kg, p.o.) inhibited the reduction of fibrinolytic activity and erythrocyte deformability, the decrease in erythrocyte counts and the increase in connective tissue of the thoracic artery in a chronic inflammatory model, adjuvant-induced arthritis. However, JR-ext was ineffective on the development of edema in the arthritic rats and on acute and chronic inflammation. JR-ext inhibited the reduction of erythrocyte deformability, but not the decrease of coagulative factors in a thrombosic model, endotoxin-induced disseminated intravascular coagulation (DIC). JR-ext also showed a promoting effect on erythrocyte deformability and fibrinolytic activity in intact rats. These results suggest that orally administered JR-ext can prevent an inducement of impediment in the peripheral microcirculation of various chronic diseases through the improvement of hemorheology.