Abstract: The alkaloid extracted from the rauwolfia roots collected from Kwangtung, Yunnan and Kwangsi were compared with that from Hainandao for the hypotensive effect and toxicity. All of them given intravenously to anesthetized dogs at 0.5—1 mg/kg produced a remarkable and sustained fall of blood pressure. The pulse rate decreased, while the respiratory rate increased. Their influence on the pressor effect of adrenaline varied from a potentiation to a reversal. The blood pressure of all hypertensive dogs which received a daily oral dose of 2—10 mg/kg of either one of the alkaloid dropped remarkably. Most animals showed sedation, lethargy, drop of eye-lids, relaxation of nictitating membrane and constriction of the pupil. Some had tremors and soft stools. The side effects produced by the Kwangtung alkaloid were most severe, those of the Yunnan alkaloid were next, while those of the Kwangsi alkaloid produced much less side effects. The LD₅₀ of the alkaloid for mice by oral route have been estimated as follows: Hainan, 0.82±0.005 g/kg; Kwangtung, 1.30±0.053 g/kg; Yunnan, 1.15±0.003 g/kg; Kwangsi, 0.69±0.028 g/kg.