Abstract: In anaesthetized or unanaesthetized animals (cats, rabbits, and rats) oral administration, or intraperitoneal injection of a refined extract of the fruit of Gardenia florida L. at the dosage of 10-13g/kg produced a significant fall of arterial pressure and on the average the reduction amounted to 43.34%. In the lapse of about 4-5 hours; the blood pressure recovered gradually. The respiratory amplitude and rate were increased slightly, at the time when the blood pressure was at its lowest. It produced a slowing of heart beat, but did not decrease the contraction of heart muscle. This extract had no ganglion-blocking, histamine liberating, sympatholytic actions and its hypotensive effect was not influenced by intravenous injection of procaine; however, the hypotensive effect was eliminated by vagotomy or atropinsation. These facts indicated that its hypotensive action is closely related to the efferent nerve of the vagus. It increased the contraction of isolated small intestine (rabbits, rats) in the concentration of 2.5×10^-4, but reduced or abolished intestinal activity in the concentration of 2×10^-2. In mice, the acute LD₅₀ after intraperitoneal injection of Gardenia florida L. was found to be 27.45g/kg.