Introduction: Viral infections are considered the most frequent cause of myocarditis and dilated cardiomyopathy (DCM). Material and methods: We investigated the changes in viral presence and the impact of viral genome persistence in the myocardium on echocardio-graphic parameters, functional status and some laboratory parameters in a 6-month follow-up. Fifty-four patients with recent onset DCM, left ventricular ejection fraction < 40% and biopsy-proven myocarditis (> 14 mononuclear leukocytes/mm(2) and/or > 7 T-lymphocytes/mm(2)) were enrolled. Polymerase chain reaction (PCR) was performed to detect pathogens in the myocardium. Patients were divided according to the administered therapy: standard heart failure medication (46 patients) and immunosuppressive therapy (8 patients). Results: In the standard heart failure medication group viral clearance was observed in 13 patients and viral persistence in 24 patients in the follow-up period. Comparing both groups, there was no statistically significant difference - LVEF improvement of 12.0 +/- 11.4% vs. 18.3 +/- 12.6%, decrease in NYHA class of 0.7 +/- 0.7 vs. 1.0 +/- 0.7, decline in NT-proBNP of 1335 +/- 1933 ng/I vs. 1942 +/- 3242 ng/I and decrease in infiltrating leukocytes of 11.1 +/- 15.8 vs. 6.7 +/- 23.0 cells/mm(2) and T-lymphocytes of 5.8 +/- 15.1 vs. 1.8 +/- 10.9 cells/mm(2) (all p = NS). A decrease in PCR positive patients from 37 to 29 was observed. The number of PVB19 positive PCR findings decreased from 5 to 4 in patients with immunosuppressive therapy. Conclusions: A decrease in the number of positive PCR findings in control endomyocardial biopsy was observed. Viral genome persistence was not associated with worse outcome in short-term follow-up.