Enteroviral RNA (EV-RNA) was detected in endomyocardial tissue by means of retrotranscription and polymerase chain reaction (RT-PCR) followed by slot-blot hybridization. The myocardial biopsy specimens studied were taken at the time of heart transplantation from 15 patients with dilated cardiomyopathy (DCM) and from 10 patients with ischemic cardiomyopathy (ICM). Specimens from 18 (72%) of the 25 patients were positive for EV-RNA, whereas no control specimens (myocardial specimens from 29 healthy organ donors and atrial specimens from 15 patients with acute myocardial infarction treated by anatomic bypass) yielded evidence of EV-RNA. The rates of EV-RNA detection for the two groups requiring heart transplantation did not differ significantly (66.7% vs. 80.0%; chi 2 test). Our findings support a link between enteroviral infection in both DCM and ICM and suggest a pathogenic role for the enteroviruses.