In Epstein-Barr virus (EBV)-positive Burkitt lymphoma (BL) the role of EBV in the translocation and deregulation of the MYC oncogene remains unknown. By utilizing an EBV-negative BL (BJAB) and several EBV-positive sublines derived from it by in vitro infection, it was possible to show that the presence of the virus was associated with altered expression and copy number of MYC. In the EBV-negative BJAB line, the level of MYC transcripts declined progressively as cells approached the stationary phase of growth. In contrast, in EBV-infected BJAB cells MYC expression remained elevated as cells entered stationary phase. This effect on MYC expression was reversibly linked to the presence of the virus. Furthermore, following EBV infection of BJAB cells by two different strains of EBV, amplification of MYC in association with the appearance of a homogeneously staining region on chromosome 8 at the mapped location of MYC had occurred. These studies suggest that both the deregulation of MYC transcription and the chromosomal rearrangement in the region of the MYC locus in this B-cell line may have occurred as a result of EBV infection.