Abstract: The inotropic and toxic effects of peruvoside and neriifolin isolated from The-vetia nerrifolia Juss were studied in anesthetized cats and guinea pigs as well as on the isolated heart and left atria of the guinea pig and were compared with those of ouabain and strophanthin K. The cardiac performance of sodium pentobarbitalinduced heart failure in cats or guinea pigs was improved during intravenous infusion of all four cardiac glycosides. Administration of peruvoside and neriifolin increased the LV dp/dt max, LVSP and MAP, and decreased the LVEDP and CVP, while the heart rate was either without significant change or slight increase. The peak effects of the two cardiac glycosides were similar to those of ouabain and strophanthin K, but the safety margin of peruvoside was about twice that of the other three glycosides. In Langendodff's heart of the guinea pig, the positive inotropic effect Of neriifolin and peruvoside was more obvious than that of ouabain at equal toxic doses(1 or 2% MLD in guinea pig),while the cardiotonic effects of these three drugs on the isolated left atrium of guinea pig were similar.