Aim. To compare the most significant architectonic parameters of peripheral blood cell subpopulations in patients with different variants of an autoimmune myocarditis (AIM) course and their clinical value in therapeutic practice. Material and methods. Blood cell subpopulations were studied with flow cytometry in 99 blood samples from patients having different AIM variants and myocardiosclerosis as well as in 40 healthy donors. Results. Severe (malignant) AIM was characterized by growing indices of T-/B lymphocyte activation, expression of activation markers on the cells of both differentiation lines, disproportions in composition of subpopulations of the immunoregulatory cells, parallel rise in specific weight of dendritic cells, reduced intensity of apoptosis of autoreactive T-lymphocytes. In benign AIM marked immunopathology was not found. This group can be considered as a separate variant of AIM course necessitating an individual approach to planning pathogenetically sound therapeutic and rehabilitation measures. Conclusion. The study of activation markers expression on peripheral blood cells is superior to the study of endomyocardial biopsies providing a non-invasive method of immunodiagnosis.