We investigated the possible relationship of Epstein-Barr virus to the development of subendocardial lymphocytic infiltrates. In situ hybridization for Epstein-Barr virus genomic sequences was performed in 22 heart biopsy specimens with subendocardial infiltrates for 19 heart transplant patients. Epstein-Barr virus genomic sequences were not detected in the lymphocytes or myocytes in any of the heart biopsy specimens. We conclude that Epstein-Barr virus is not related to the development of subendocardial lymphocytic infiltrates.