The Epstein-Barr virus(EBV) is the causative agent of certain types of lymphoma and some epithelial neoplasms such as undifferentiated nasopharyngeal carcinoma, and there is recently increasing benign and malignant diseases associated with EBV. When there is the EBV infection, the latent membrane protein-1(LMP 1) play an important role of the malignant transformation. The bcl 2 shows the unique functional role of blocking programmed cell death(apoptosis) independent of affecting proliferation, appears to constitute a member of a new category of oncogenesregulators of programmed cell death. The purpose of this study was to examine the relationship between EBV and nasopharyngeal cancers through EBV-encoded small RNA(EBER 1) in situ hybridization techniques, to examine the possibility of bcl 2 as a new category of oncogenes and to examine the relationship between EBV and bcl 2 expression in the forty two nasopharyngeal cancers. And we used 10 cases of normal nasopharyngeal tissue as the positive control group. For these purpose, paraffinembedded tissues were subjected to in situ hybridization and immunohistochemistry techniques. Following results were obtained : 1) The EBV was detected in 18(90%) out of 20 cases of nasopharyngeal undifferentiated carcinoma, 14(70%) out of 20 cases of nasopharyngeal squamous cell carcinoma. 2) The LMP 1 was detected in 2(10%) out of 20 cases of nasopharyngeal undifferentiated carcinoma, in 1(5%) out of 20 cases of nasopharyngeal squamous cell carcinoma. 3) The bcl 2 was detected in 37(88.09%) out of 42 cases of nasopharyngeal cancer, the rate of bcl 2 expression was more higher in EBER 1-positive cases. In conclusions we found that the EBV was closely related to nasopharyngeal cancer, especially undifferentiated type, and there was a close relationship between EBV and bcl 2 expression in nasopharyngeal cancers.