As in radiation-induced cancer, post-irradiation sudden deafness (PISD) is defined as sudden onset deafness in patients post-irradiation. Fifteen nasopharyngeal carcinoma (NPC) patients with PISD were enrolled in this study. The mean interval from the completion of irradiation to the occurrence of PISD was 12 years. Seven had total deafness, seven had profound hearing loss, and one had moderate hearing loss. Nine out of 15 (60 per cent) patients experienced hearing recovery within three months after treatment. In conclusion, PISD is a late complication in NPC patients post-irradiation. The causative mechanism is theorized as vascular insufficiency.