Abstract: In the "Charcaol test", the ID5O of loperamide was found to be 0.957 mg/kg s. c. loperamide is an agent devoid of morphinelike behavior, even at toxic dose level （80mg/kg s. c. ）. It has a potent antagonist action upon histamine-induced contraction of the guinea-pig ileum and can decrease the amplitude and number of spiks of duodenum, ejjunum and ileum myoelectrical activity. It is also a potent and safe inhibitor of gastro-intestinal motilily.