Objective: To investigate whether the nasopharyngeal squamous cell carcinoma or keratinizing squamous cell carcinoma (KSCC) is also closely associated with Epstein-Barr virus infection as nasopharyngeal non-keratinizing carcinoma does. Methods: The Epstein-Barr virus (EBV) DNA and its gene expression products, including EBNA-1, EBNA-2, EBERs, LMP-1, ZEBRA, EA-D, VCA and MA were detected in 38 nasopharyngeal KSCCs using PCR Southern blotting hybridization, in situ hybridization and immunohistochemistry. Results:(1) The EBERs positive cancer cells could be found in 37 KSCCs (97.4% , 37/38). (2) Most undifferentiated and poorly differentiated cancer cells of these 37 KSCCs expressed EBNA-1 and EBERs; and LMP-1 positive cells could be found in 21 specimens (56.8% , 21/37). (3) A few of ZEBRA positive or/and EA- D positive cancer cells were found in 23 out of 37 KSCCs (62.2% , 23/37). (4) Several of more differentiated or keratinizing cancer cells expressed VCA or/and MA in 22 of 37 KSCCs (59.5% , 22/37). Conclusions:(1) KSCCs of the nasopharynx in the south of China are also consistently, not occasionally, associated with EBV infection as non-keratinizing carcinomas (NKCs) do; (2) The majority of undifferentiated and poorly differentiated cancer cells in KSCCs are always infected with EBV in type II latency, mainly expressing EBNA-1, EBERs, and LMP-1, and a small number of them may express the abortive immediate early and early viral proteins (ZEBRA ＆ EA-D); (3) The more differentiated or keratinizing cancer cells infected with EBV in KSCCs might complete its production cycle and express late viral proteins (VCA or/and MA).