In order to find out the pharmacologically active but less toxic compounds than piperine, the actions of several amide derivatives of 5-phenyl-2, 4-pentadienoic acid on the CNS depressant activities were examined. The nine amide derivatives were investigated by using ICR mice as an experimental amimals on acute toxicities, anticonvulsant, sedative, analgesic and antipyretic effects. In the case of acute toxicities, all derivatives were weaker than piperine except compound III. Compound I showed strong anticonvulsant activity. On the other hand, compound I, III and IV significantly prolonged the sleeping time induced by hexobarbital in mice. Compound I, III and IV exhibited better analgesic effect than aspirin while compound II, V, VII and IX showed similar antipyretic activity to aspirin.