This study was performed in dogs and chickens to observe differences of responses by species of animals to hypotensive action of Siegesbeckiae Herba, using its ethanol extract. Siegesbeckiae Herba e ethanol extract (SGEE), when injected into the vein of dogs or chickens, elicited depressor actions in both a animals. The hypotensive effects of SGEE in dogs and chickens were markedly inhibited by the pretreatment of atropine, but not affected by bethanidine, propranolol and diphenhydramine. Phentolamine significantly weakened the action of SGEE in dogs, but did not alter the action of SGEE in chickens. SGEE inhibited the pressor action by norepinephrine or carotid artery occlusion, whereas it did not change the pressor action b by angiotensin in dogs.