Objective:To evaluate the efficacy of computed tomography (CT)-guided implantation of radioactive ~(125)I seeds in the treatment of residual foci of nasopharyngeal carcinoma after radiotherapy.Methods:Twenty-five nasopharyngeal carcinoma patients who had residual foci after radiotherapy were implanted radioactive ~(125)I seeds from January 2007 to January 2008 in our hospital. Three-dimensional treatment planning system (TPS) was used to calculate the quantity and total dosage of ~(125)I seeds. The radioactive ~(125)I seeds were implanted into residual foci under CT guidance. The dosage distribution of radioactive ~(125)I seeds were verified after surgery. The nasopharyngeal endoscopy CT scans were performed at 3, 6, and 12 months after surgery and the short-term efficacy and adverse reaction were evaluated. Results:Out of the 25 patients, 20 patients had complete response (CR), 2 patients had partial response (PR), 2 patients had no change (NC), and 1 patient had progressive diseases (PD). The overall effective rate (CR+PR) was 88.0%. All patients had no serious postoperative complications. Conclusion:CT-guided implantation of radioactive ~(125)I seed was an effective and safe method in the treatment of the residual foci of nasopharyngeal carcinoma after radiotherapy.