Background : Aside from enteroviruses, various viruses such as parvovirus B19 (PVB19) may be a new and important candidates for myocarditis and non-ischemic dilated cardiomyopathy (NDCM). There were few studies on the prevalence of viral genomes in korean population. The purpose of this study was to investigate the presence of viral genomes by polymerase chain reaction (PCR) in endomyocardial tissues (EMBs) from patients with NDCM. Methods : EMBs were obtained from 39 patients with NDCM. PCR and reverse transcription-PCR were performed to detect the genomes of enterovirus (EV), adenovirus, PVB19, cytomegalovirus, Epstein-Barr virus, herpes simplex virus (HSV), human herpesvirus 6 (HHV6). EMBs from 31 patients were assessed by immunohistochemical staining (IHCS) for CD3, CD45, HLA-DR, ICAM-1, VCAM-1, CD62-E, LFA-3. Results : Mean age of patients were 47 (range: 17-69) and 23 (59%) were male. Patients with duration of symptoms less than 6 months were 29 (74%). Fifteen (38%) of the 39 EMB were positive to viral genomes: EV = 1 (2.6%), PVB19 = 11 (28.2%), HHV6 = 3 (7.7%), HSV2 = 1 (2.6%), including 1 case with multiple infection (PVB19 + HHV6). Ten (55.6%) of 18 EMBs without viral genomes and 8 (61.5%) of 13 EMBs with viral genomes were positive to IHCS for cellular or adhesion makers. Among 33 patients with follow-up echocardiography, improvement of left ventricular systolic function (increase of more than 10% of ejection fraction) occurred in 8 (73%) of 11 patients positive to viral genomes, but in 11 (50%) of 22 patients negative to viral genomes. Six patients died during the follow-up period. Two patient was positive to PVB19 and 4 patients had no viral genomes in EMB. Conclusion : PVB19 genome was most frequently detected in EMBs from patients with NDCM in this population.