Abstract: Objective: To investigate the incidence rate and clinical characteristics of radiationinduced malignan-cies in nasopharyngeal carcinoma patients and to analyze factors that impact latency and prognosis. Methods: Data from atotal of 39,118 patients with nasopharyngeal carcinoma who underwent radical radiotherapy as the initial treatment be-tween February 1964 and December 2003 were collected. Characteristics and outcome of 198 patients with carcinoma in-duced after radiotherapy were analyzed retrospectively. Results: The incidence rate of radiationinduced malignant tumorin these patients was 0.5%. The median latency was 108(36360) months. The oral cavity was the most frequently involvedsite (N=107, 54.0%). Squamous cell carcinoma was the most frequently observed pathology type (N=137, 69.2%), followedby fibrosarcoma (N=21, 10.6%) and osteosarcoma (N=12, 6.1%). Latency was related to radiation pattern, radiation dose,chemotherapy, and the patients'age at which they received radiotherapy. Multivariate analysis showed that the risk factorsthat independently influenced the overall survival were gender and relapse of induced carcinoma. Conclusion: The malig-nant tumor most frequently induced by radiotherapy for nasopharyngeal carcinoma is carcinoma in the oral cavity. Reduc-ing the radiation dose to the oral cavity will help decrease the incidence of radiationinduced malignancies after radiother-apy for nasopharyngeal carcinoma.