Abstract: Objective :To study the correlation between apoptosis, proliferating cell nuclear antigen (PCNA) and c-myc expression, and the relationship between they and radionsensitivity in nasopharyngeal carcinoma (NPC). Methods :Thirty me patients proven be nasopharyngeal squamous cell carcinoma were eligible enter into this study. All patients in this study were biopsied from nasopharynx for two times, first biopsy's samples were performed before irradiation,and second ones were takenafter receiving radiation dose of 1520CGy. Apoptosis cells were determined by the terminal deoxynu cleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method. PCNA and c-myc were deter-mined by immunohistochemical S-P staining technique. Results :The expression of c-myc before radiotherapy was negative relationship with Spontaneous AR of tumor cell, and was positive relationshipwith PCNA. However, the expression of c-myc after radiotherapy was positive relationship with AR of radiation-induced and was negative relationship with PCNA after radiation (P<0.01). Radiosensitivity ofradiation-induced and was negative relationship with PCNA after radiation (P<0.01). Radiosensitivity of tumor cells was positively associated with the PCNA expression before radiation, spontaneous AR, AR of radiation-induced and down values of PCNA after radiation (P<0.01), and was not associated with and c-myc(P>0.05). Conclusions :The apoptosis and PCNA are closely related with the radiosensitivity in NPC, whereas c-myc expressions plays a modulated role for apoptosis and cell proliferation.