Objective: To evaluate the long-term survival outcomes and toxicity of a larger series of patients with non-metastatic T4 classification nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiotherapy (IMRT).Materials and methods: From March 2004 to June 2011,335 non-metastatic T4 classification NPC patients treated by IMRT were analyzed retrospectively.Treatment induced toxicities were scored according to the Common Terminology Criteria for Adverse Events version 3.0.Results: With a median follow-up time of 53.6 months (range, 2.8-114.9 months), the 5-year local failure-free survival (LFFS), regional failure free survival (RFFS), distant failure-free survival (DFFS), and overall survival (OS) were 84.1%, 92.2%, 74.1%, and 63.0%, respectively.At their last follow-up visit, 118 patients (35.2%) had developed treatment failure.Distant metastasis was the major failure pattern after treatment.The most common toxicities were mainly in grade 1 or 2.Concurrent chemotherapy failed to improve survival rates for patients with T4 classification NPC.Conclusion: The results of T4 classification NPC treated by IMRT were excellent, and distant metastasis was the most commonly failure pattern.Treatment-related toxicities were well tolerable.The role of concurrent chemotherapy for T4 classification NPC needs to be further investigated in the era of IMRT.