Myocarditis is an important disease that can lead to dilated cardiomyopathy (DCM). Using the polymerase chain reaction (PCR), we examined whether viral genomes were present specifically in the hearts of viral myocarditis or DCM patients in our autopsy series and compared the results with their clinicopathological features. We applied three different criteria of myocarditis to fully describe the histological features. The presence of a viral genome was detected by PCR but was not specific in DCM or myocarditis. PCR might be helpful in the diagnosis of viral myocarditis, when combined with other clinical information.