Epstein-Barr virus (EBV) obtained directly from the oropharynx was used to detect viral DNA deleted for the EBV nuclear antigen 2 (EBNA2)-encodinggene that is essential for lymphocyte transformation. By polymerase chain reaction analysis, the deletion was found in virus from 5 of 33 healthy adult donors and 11 of 12 patients with concurrent human immunodeficiency virus infection. Lymphoblastoid cell lines that produce standard transforming EBV also harbored EBNA2-deleted virus in cells permissive of EBV replication. In vitro infectivity studies indicated that the DNAis packaged and transmissible, with biologic properties similar to those of a laboratory mutant, P3HR-1, which also lacks the EBNA2gene. These findings, obtained from productively infected cell systems, provide evidence for the existence in nature of a transformation-incompetent EBVv ariant that may facilitate EBV persistence and the emergence of reactivation diseases.