Basing on the collation of data of histochemical and electron-microscopic investigations of the myocardium of rabbits under conditions of diphtherial intoxication and in blocade of the lipolysis processes in the intact and damaged heart, the authors singled out three ways of utilization of lipids by the cardiac muscle. The first way is associated with adsorption of fatty acids from the circulating blood. This way depends on catecholamines and is blocked with nicotinic acid. The second way is determined by splitting of myocardial triacylglycerols. It does not depend on concentrations of catecholamines and can be blocked only following prolonged exposure to nicotinic acid. The third way is associated with intensity of functioning of mitochondria; destruction of the latter brings about liberation of membrane phospholipids which later are transformed into nonesterified fatty acids. This way does not depend on catecholamines and can be inhibited by acid lipids accumulating in the myocardium as a result of impairment of utilization of these lipids.