Molecular pathologic investigation of endomyocardial biopsy specimens from 26 patients with peripartum cardiomyopathy revealed viral genomes (parvovirus B19, human herpes virus 6, Epstein-Barr virus, and human cytomegalovirus) in 8 patients (30.7%) that were associated immunohistologically with interstitial inflammation. These findings indicate a high prevalence of virus-associated inflammatory changes in peripartum cardiomyopathy.