Abstract: Objective To investigate the expression of KAI1／CD82 mRNA and CD82 protein in nasopharyngeal carcinoma, and the relationship of them with clinical features. Methods By immunohistochemical SP method， the CD82 protein expression was detected in 70 cases of nasopharyngeal carcinoma and 30 cases of normal nasopharyngeal tissues； By reverse transcription polymerase chain reaction （RT-PCR）， the KAI1／CD82 mRNA expression in 28 cases of nasopharyngeal carcinoma and 15 cases of normal nasopharyngeal fresh tissue were tested. The relationship of KAI1／CD82 mRNA and protein with clincopathological features were statistically analyzed. Results The positive expression rate of KAI1／CD82 mRNA in nasopharyngeal carcinoma was 42.9％ （12／28）， lower than 73.3％ （11／15） in the normal nasopharyngeal tissues（P＞0.05）. The positive expression rate of CD82 protein in nasopharyngeal carcinoma was 44.3％ （31／70）， lower than 70.0％ （21／30） in normal nasopharyngeal tissues（P＜0.05）. In nasopharyngeal carcinoma， the expression of KAI1／CD82 mRNA and CD82 protein was not related to the gender， age， histological type and T stage （P＞0.05）， but related to lymph node metastasis （P＜0.05）. The expression rates of KAI1／CD82 mRNA and CD82 protein in the group without lymph node metastasis were 85.7％ and 68.4％， were higher than 28.6％ and 35.3％ in the group with lymph node metastasis, and the difference were statistically significant （P＜0.05）. The expression of KAI1／CD82 mRNA and CD82 protein in the subgroups of the stage N1N3 had no significant difference（P＞0.05）. Conclusion The downregulation of KAI1／CD82 mRNA and CD82 protein expression is found in nasopharyngeal carcinoma. KAI1／CD82 can inhibit the process of nasopharyngeal carcinoma invasion and metastasis. So coexamination of KAI1／CD82 mRNA and CD82 protein may be a biologic marker for diagnosis and prognosis of nasopharyngeal carcinoma.