In this study the effect of water extract of Viticis rotundifoliae Fructus(VRE) on the blood pressure of the rabbit was investigated. The results of the experiment are as follows. 1. VRE produced a fall of blood pressure, exhibiting dose-action curve in the rabbit. 2. The depressor effect of VRE was inhibited by atropine and chlorisondamine, potentiated by physostigmine, and then potentiated slightly by bethanidine. 3. Effect of VRE was not influenced by propranolol and cyproheptadin. The above results indicate that hypotension of VRE is produced by stimulation of parasympathetic nervous system induced centrally.