Abstract: A crystalline glucoside, oleandrin, m.p. 250.5—251.5℃, a23.5=-47.9, was isolated from Nerium indicum Mill. by Chen Wei-xin (陈维新). Comparison of the cardiotonic actions between oleandrin and digitoxin was studied as follows: 1. By experiments on frogs' and rabbits' hearts in situ, isolated guinea pigs' hearts and EKG on cats, oleandrin produced cardiotonic effects similar to those of digitoxin. 2. By experiments on rabbits' hearts in situ and isolated guinea pigs' hearts, it was found that the phases of action, such as the time on onset, maximal effect, regression, and disappearance of these two drugs were alike. 3. The pigeon units of oleandrin and digitoxin according to the Chinese Pharmacopeia were found to be 0.44±0.04 and 0.77±0.08 mg/kg (S. D.), respectively.