Abstract: A tincture was prepared from the bark of Periploca calophylla (Wight.) Falconer (Fam. Asclepiadaceae) which grow wild in the west part of Yunnan Province in China. After alcohol was removed by evaporation, the residue was dissolved in distilled water, and used in experiments. The drug was demonstrated to be cardiotonic by experiments on frog and rabbit heart in situ, isolated guinea pig heart, and on EKG in cats. The pigeon units of the bark of Periploca calophylla according to the Chinese Pharmacopoeia was found to be 31.86±1.62 (S. D.) mg/kg.