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AIM: To understand the expression of latent and lytic genes of Epstein-Barr virus (EBV) in EBV-associated gastric carcinoma (EBVaGC) and to explore the relationship between EBV-encoded genes and development of EBVaGC at molecular level.METHODS: One hundred and seventy-two gastric carcinoma tissues and 172 corresponding para-carcinoma tissues were tested for EBV genome by polymerase chain reaction (PCR)-South blotting. EBV-encoded small RNA (EBER)1 of the PCR positive specimens was detected by in situ hybridization (ISH). Gastric carcinomas with positive EBER1signals were classified as EBVaGCs. RT-PCR and South hybridization were applied to the detection of expression of nuclear antigen (EBNA) promoters (Qp, Wp and Cp),EBNA 1 and EBNA 2, latent membrane proteins (LMP) 1,2A and 2B and lytic genes (immediate early genes BZLF1and BRLF1, early genes BARF1 and BHRF1, late genes BcLF1and BLLF1) in EBVaGCs.RESULTS: Eleven EBV positive samples existed in gastric carcinoma tissues (6.39%). No EBV positive sample was found in corresponding para-carcinoma tissues. The difference between EBV positivity in carcinoma tissues and corresponding para-carcinoma tissues was significant(x2 = 9.0909, P = 0.0026). Transcripts of Qp and EBNA1were detected in all the 11 EBVaGCs, while both Wp and Cp were silent. EBNA2, LMP1 and LMP2B mRNA were absent in all the cases, while LMP2A mRNA was detected in 4 of the 11 cases. Of the 11 EBVaGCs, 7 exhibited BcLF1 transcripts and 2 exhibited BHRF1 transcripts. The transcripts of BZLF1and BARF1 were detected in 5 cases, respectively. No BLLF1and BRLF mRNA were detected.CONCLUSION: The latent patt of EBV in gastric carcinoma corresponds to the latency Ⅰ/Ⅱ. Some lyric infection genes are expressed in EBVaGCs tissues. BARF1 and BHRF1genes may play an important role in tumorigenesis of gastric carcinoma.