Effects of Astragali Radix Water Extract (ARWE) on the blood pressure were investigated in the whole rabbit and the spinalized rabbit. ARWE, when administered into the ear-vein or lateral ventricle, produced a fall in the blood pressure in the whole rabbit, but intravenous ARWE in the spinalized rabbit did not elicite the hypotensive action. Pretreatments with chlorisondamine, guanethidine, phentolamine and cyproheptadine in the whole rabbit weakened the depressor action of ARWE. The hypotensive action of the whole rabbit to ARWE was not influenced by the pretreatment of the animals with diphennylhydramine, propranolol, and vagotomization, whereas inhibited by atropine. ARWE did not affect the pressor response by angiotensin. However, it enhanced the hypertensive action by norepineprine and reduced the elevation in the blood pressure by carotid occlusion in the whole rabbit. These experimental observations suggest that ARWE may cause the depressor response via mechanisms of the central sympathetic blocking action, cholinergic action by peripheral origin and serotonin-like action.