The sum of bufadienolides (bacagin) isolated from the poison of Bufo viridis toad occurring in Central Asia produces a selective strophanthin-K-like action upon the heart function, increasing myocardial contractility, retarding cardiac rhythm, and positively influencing the parameters of myocardial metabolism. The mechanism of realization of the positive ionotropic effect of bacagin is probably related to the ability of increasing the basal level of cytosol calcium at the expense of inhibiting the activity of Na+/K(+)-ATPase and, to some extent, Ca(2+)-ATPase in endoplasmic reticulum.