We had reported that patients with idiopathic unilateral auditory and/or vestibular symptoms who had ipsilateral displacement of the basilar artery (BA) at a significantly high incidence were evaluated with axial view T2-weighted MR images (MRI). In this study, the distance of BA displacement from the midline was measured in 25 patients with idiopathic unilateral auditory and/or vestibular symptoms (15 females and 10 males; mean age, 63.0 years). MRI of 17 patients with sudden deafness or vestibular neuronitis (9 females and 8 males; mean age, 53.9 years) were used as controls. The mean distance of 5.5 mm in the 25 patients was significantly further than that of 2.9 mm in the controls. This result highly suggests that idiopathic unilateral auditory and/ or vestibular lesions developed as a result of sclerotic change of the vertebrobasilar artery.