A 54-year-old man had a slowly progressive bilateral brachial plexopathy 17 months after surgery and radiation therapy for a stage IV supraglottic carcinoma. MR imaging at presentation showed a symmetric pattern of parascalene and interscalene hyperintense signal on T2-weighted images and after contrast enhancement. Although hyperintense signal has been more often associated with recurrent tumor than with delayed radiation injury or fibrosis, the location and pattern of the signal abnormalities suggested a diagnosis of radiation-induced plexopathy. This diagnosis was confirmed by the relative stability of the neurologic and MR findings 30 months after treatment.