Immunohistochemical and molecular-pathologic techniques have improved the diagnosis of myocarditis as compared with conventional histologic staining methods done according to the Dallas criteria. Most investigations were carried out on adults, and only a few authors investigating childhood deaths applied these modern methods, used for diagnosing myocarditis. We report on four children under one year of age, who suddenly died without prodromal symptoms. Their deaths were attributed to SIDS (sudden infant death syndrome). Immunohistochemical (LCA, CD68, CD45R0, MHC-class-II-molecules, VP1-capsid-protein of enteroviruses) and molecular-pathologic (RT-PCR) investigations, however, suggested that death was caused by a coxsackie-B3-myocarditis. In the future, these methods should be used for investigating cases with suspicion of SIDS.