The aim of the study: to investigate the effects of glucocorticoids on the activity of immunologic biomarkers and the persistence of cardiac arrhythmias in patients with severe myocarditis. Object and methods of the study. The study included 112 patients with severe myocarditis, who were divided into 2 groups: the 1st group included 72 patients who received pathogenetic therapy with glucocorticoids, the 2nd group included 40 patients who did not receive glucocorticoids treatment. All patients underwent determination of the content of immunological biomarkers, 24-hour electrocardiography monitoring and cardiac magnetic resonance contrast. The examination was performed in the 1st month from the onset of myocarditis, after 6 and 12 months of observation. Results. In patients with severe myocarditis after completing a course of immunosuppressive therapy with glucocorticoids, a significant decrease in the concentration of pro-inflammatory biomarkers — tumor necrosis factor-α, interleukin-1β and C-reactive protein — was determined after 6 and 12 months of observation, which was associated with a 23,4% lower number of left ventricle segments with inflammatory changes after 6 months and with a 34,9% lower total volume of left ventricle damage after 12 months according to the results of cardiac magnetic resonance, which was accompanied by a lower frequency of persistence of ventricular arrhythmias compared to patients who did not receive such therapy. Conclusion. The administration of glucocorticoid therapy to patients with severe myocarditis was associated with a decrease in the incidence of ventricular arrhythmias — paroxysms of non-sustained ventricular tachycardia and ventricular extrasystoles after 6 and 12 months of follow-up.