Abstract: Objective : To investigate the relationship between the expression of bcl-2 and bax protein and the radiosensitivity of nasopharyngeal carcinoma (NPC). Methods : The expression of bcl-2 and bax protein was detected by immunohistochemical method in 51 biopsy specimens prior to radiotherapy of NPC. Results : The positive expression of bcl-2 and of bax protein were both demonstrated in 47 out of 51 cases (92.2%)of NPC. The positive expression between bcl-2 and bax protein was highly correlated (P<0.05). The bcl-2 protein expression was negatively correlated with the radiosensitivity of NPC (P<0.05), while the bax protein expression was not correlated with the radiosensitivity of NPC (P>0.05). There was a negatively correlation between bcl-2/bax ratio and the radiosensitivity of NPC (P<0.05). Conclusion : The bcl-2 protein and the bcl-2/bax ratio were the important parameters reflecting the radiosensitivity and predicting the radiotherapeutic effect of NPC, while the bax protein could not be taken as an independent parameter to predict radiosensitivity of NPC.