Background: To evaluate efficacy and side effects of glycididazole sodium (CMNa) combined with chemotherapy (cisplatin plus 5-FU/folic acid, PLF) and radiotherapy in treating patients with locally advanced nasopharyngeal carcinoma. Materials and Methods: Patients with III~IV stage nasopharyngeal carcinoma (NPC),were randomly divided into treatment group (46 patients) and control group (45 patients). Both groups received radiotherapy concomitant with PLF chemotherapy. The treatment group at the same time cwas given CMNa ($800mg/m^2$ before radiotherapy), by l h intravenous drip, three times a week. Results: When the dose of radiation was over 60 Gy, complete response rates of nasopharyngeal tumor and lymph node metastases in treatment group were significantly higher than in the control group (93.5% vs 77.8%; 89.1% vs 93.5%, p<0.05). Three months after radiotherapy, complete response rate of nasopharynx cancer and lymph node metastases in treatment group was both 97.8%, again higher than in the control group (84.4% and 82.2%) (p<0.05). In the treatment group, 1, 3, 5 year disease-free survival rates were 95.7%, 86.7% and 54.5%; and in control group, the corresponding disease-free survival rates were 93.3%, 66.2% and 38.6%, respectively, the difference being statistically significant (log-rank =5.887, p=0.015). One, 3, 5 year overall survival rates in two groups of patients were 97.8%, 93.5%, 70.4% and 95.5%, 88.07%, 48.4%, respectively, again with a statistically significant difference (log-rank=6.470, p=0.011). Acute toxicity and long-term radiotherapy related toxicity in the two groups did not differ (p>0.05). Conclusions: Glycididazole sodium could improve curative effects without increasing adverse reactions when treating paitents with locally advanced nasopharyngeal carcinoma.