Objective To evaluate the impact of reducing clinical target volume (CTV) on the efficacy of intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC) . Methods Between August 2003 and March 2007, 380 NPC patients were treated with IMRT with reduced CTV.CTV1, defined as high risk region, included GTV +5 - 10 mm margin and the entire nasopharyngeal mucosa +5 mm submucosal volume; CTV2, designed for potentially involved regions, included the nasopharyngeal cavity (limited to the posterior part of nasal cavity only), maxillary sinus (limited to 5 mm anterior to the posterior nasal aperture and maxillary mucosa), pterygopalatine fossa, posterior ethmoid sinus,parapharyngeal space, skull base, anterior third of clivus and cervical vertebra, inferior spheniod sinus and cavernous sinus and internal group of retropharyngeal lymph nodal regions from the base of skull to cranial edge of the second cervical vertebra. The prescription dose was: GTV 66. 00 -69. 75 Gy/30 - 33 f, CTV1 60. 00 -66. 65 Gy,CTV2/CTVN 54. 0 -55.8 Gy. 308 patients with stage Ⅲ or Ⅳ diseases also received cisplatin-based neoadjuvant chemotherapy. Results The follow-up rate was 100%. 145 patients were followed-up to 3 years. The 3-year estimated local control, regional control, metastasis-free survival,disease-free survival and overall survival rates were 94. 9%, 97.4%, 86. 2%, 80. 9% and 89. 0%,respectively. Multivariate analysis revealed that N-classification was a significant prognostic factor for metastasis-free survival (x2 = 20. 80, P = 0. 001), N-classification (x2 = 18. 30, P = 0. 003) and age (x2 =7. 31, P =0. 004) were independent prognostic factors for overall survival. Grade 2 xerostomia was observed in 5.6% of the patients after two years of IMRT, no Grade 3 or 4 xerostomia was observed. Local, regional,and distant failures were developed in 4. 2%, 2. 6% and 12. 1% of the patients, respectively. Conclusions The IMRT approach with reduced CTV2 provids a favorable outcome for NPC with acceptable toxicities.