We observed a potentially misinterpretable polymerase chain reaction (PCR) amplification product generated with standard primers used to detect the major breakpoint region (mbr) of chromosomal translocation t(14;18). This unexpected phenomenon was initially detected during attempts to transform follicular lymphomas in vitro with Epstein-Barr virus (EBV). Additional studies were performed using the EBV-producing cell line MCUV5, cell lines from EBV-transformed normal B-lymphocytes, and an excised lymph node from a patient with documented EBV-associated infectious mononucleosis. These samples consistently produced a 167-base pair product, which was indistinguishable from a t(14;18) lymphoma product when viewed on ethidium bromide-stained gels. Through DNA sequencing and gene bank analysis, the product was identified as a portion of the EBV genome. A mbr-specific 20-base oligonucleotide probe was able to discriminate between true translocations and the EBV-related amplifications. These results underscore the importance of employing a specific detection system, and comprehensively screening primers when working with PCR.