Despite the fact that cardioglycosides have been used in the treatment of cardiac failure for more than 2000 years, endogenous digoxin and ouabain-like substances were identified from the chemical aspect only in 1990. They are steroids, their main site of origin being the adrenals. It is assumed that they play a part in the regulation of the body fluids and sodium in the organism and participate in the regulation of cardiac activity. The stimulus which leads to their release into the blood stream are above all conditions associated with sodium and fluid retention with expansion of the intravascular volume. It is assumed that these substances participate in the pathogenesis of some types of hypertension. The authors present a general review of contemporary knowledge of endogenous digoxin and ouabain-like substances.