Objective Radiotherapy is the primary therapy for early stage nasal-type NK/T-cell lymphoma of the nasal or Waldeyer ring. This study aimed to investigate the clinical outcome of the disease treated with intensity-modulated radiation therapy (IMRT). Methods From November 2003 to June 2008, 48 patients with nasal or Waldeyer ring NK/T-ceil lymphoma underwent IMRT. The tumors were located in the nasal in 42 patients ,and the Waldeyer ring in 6. According to the Ann Arbor staging system, the disease was stage Ⅰ_E in 37 patients (77%), stage Ⅱ_E in 11 (23%). Of these patients, 22 received radiotherapy alone, the other 26 received combined chemotherapy and radiotherapy. Prescribed radiation dose was defined as a minimun dose of 95% PTV. Acute and late toxicities were scored by Radiation Therapy Oncology Group morbidity criteria. Survival probabilities were estimated using Kaplan-Meier method. Results With a median follow-up of 18 months, the 2-year local control, overall survival and progression-free survival rates were 100%, 75% and 73%, respectively. The average maximum, mean and minimum delivered doses were 62.6 Gy, 55.0 Gy and 20.3 Gy to the PTV. Only 2.4% of the PTV received less than 95% of the prescribed dose. The average maximum dose to the brain, spinal cord, optic chiasm, left optical nerve, right optical nerve, left len and right len was 43.5 Gy, 32. 7 Gy, 48.2 Gy, 50. 3 Gy, 51.3 Gy, 7. 8 Gy and 7.6 Gy, respectively. The average mean dose to the left parotid, right parotid, pituitary, left T-M joint and right T- M joint was 17. 1 Gy , 16. 5 Gy , 32. 5 Gy , 47.3 Gy and 46. 8 Gy , respectively. Acute mucositis was observed in 37% of patients with Grade 1, 41% with Grade 2, and 16% with Grade 3. Skin toxicity was observed in 78% of patients with Grade 1 and 16% with Grade 2. Acute xerestoma was observed in 65% of patients with Grade 1 and 18% with Grade 2. Conclusions IMRT provids excellent tumor target coverage and reduces the dose to the critical normal tissues such as the salivary glands. Longer follow-up is needed to assess the long-term overall survival and local control.