We analyzed the dynamics of ultrastructural changes in cardiomyocytes in experimental chronic anthracycline cardiomyopathy. Doxorubicin-induced changes in cardiomyocytes were characterized by a specific combination of ultrastructural changes, which can be regarded as markers of the development of regeneratory and plastic insufficiency. These markers include a triad of changes: deformation of the nuclei with reorganization of the nucleolar system; diffuse and small focal lysis of myofibrils (mainly fine filaments); dilatation of agranular sarcoplasmic reticulum and the intermembrane perinuclear space connected to it. The terminal stages of these disorders are degeneration of some cardiomyocytes, their apoptotic death, and resorption by mononuclear cells (processes representing successive stages in the development of regeneratory and plastic insufficiency of the myocardium).