Abstract: Objective To examine the changes of radiosensitivity of CNE1, a well differentiated squamous cell line of nasopharyngeal carcinoma (NPC), and CNE2, a poorly differentiated squamous cell line of NPC, after treatment with chemotherapeutic agents. Methods CNE1 and CNE2 cells with and without treated by adriamycin (ADM) were irradiated by X-ray and the radiosensitivity changes of ADM-treated cells were analyzed according to the cell survival curve generated by colony formation assay. Result and Conclusion Radiosensitivity of CNE1 cells increased after ADM treatment, but that of CNE2 cells decreased, suggesting that different treatment regimens should be planned for advanced squamous cell NPC of different pathological types.