Magnetic resonance imaging (MRI) and computed tomography (CT) were performed on 13 patients with clinical features of late temporal lobe damage following radical radiotherapy for nasopharyngeal carcinoma, and their results compared. MRI was undoubtedly superior in sensitivity--revealing areas of prolonged T2 relaxation time in the inferior portions of the temporal lobes in all patients, while CT failed to show any gross abnormalities in seven. In patients with large lesions well-depicted on CT, the corresponding MRI changes were comparable in shape and extent. But MRI gave an additional sign for the presence of liquefactive necrosis, and revealed lesions in the contralateral lobes in two out of three patients with unilateral CT changes. Besides obvious improvement in detection rate, the contribution of MRI to the better selection of treatment protocols, and to the understanding of the pathological process are discussed.