Abstract: Physochlaina infundibuleris Kuang has long been used in Chinese medicine as a sedative. The pharmacologic actions were as follows: (1)The acute LD₅₀ for mice was found to be 43 (28.7-64.5) g/kg when given intraperitioneally in the form of decoction. (2) In rats, by the method of motor defence conditioned reflex, oral administra- tions with 2 g/kg of the drug produced prolongation of the latent period of conditioned reflex; intraperitoneal injection of the drug (1g/kg) not only prolonged the latent period and partly abolished the conditioned reflex, but also partly disturbed the differentiation. (3) Decoction of the drug at a dose of 1-4g/kg given intraperitoneally pro- duced a marked reduction in spontaneous activity, lasting about 3-6 hours, in mice, rats, and rabbits, but did not reduce the passive activity in mice. In 6 dogs after oral administretions with 2-5g/kg of the drug, sedation emerged. (4) In mice, intraperitoncal injection of the drug (4g/kg) potentiated the hypnotic and anaesthetic effect of pcntothal, pentobarbital, and chloral hydrate, reduced the hyper- activity induced by amphetamine and caffeine, but a dose as large as 10g/kg had no effect on the amphentamine toxicity and ED₅₀ of convulsion caused by strychnine and metrazol. (5) In dogs, oral administrations with 2-5g/kg of the drug did not antagonize emesis caused by 0.2 mg/kg of apomorphine.