Standardized one-step real-time RT-PCR assay detected enterovirus RNA in cardiac biopsy samples from 4 of 20 patients suffering from idiopathic dilated cardiomyopathy (IDCM). The median viral load was 287 copies per microgram of total extracted nucleic acids, with positive- to negative-strand RNA ratios ranging from 2 to 20. These results demonstrate enterovirus persistence in the heart of IDCM patients, characterized by low viral loads and low positive- to negative-RNA ratios.