The differential diagnosis usually entertained when smooth erosions of the lateral aspect of cervical vertebrae are encountered includes neurofibroma, dermoid, teratoma, fibroma from the ligaments of the spinal column, meningocele herniating through the intervertebral foramen, and vertebral aneurysm. The authors have recently encountered an unusual instance of such bone erosion which was shown by arteriography to have been produced by a tortuous loop of the left vertebral artery. Since no reports of this entity have been uncovered by a search of the radiological literature over the past twenty years, and as no mention has been found in the radiological texts (1–3), the following case is reported. Case Report F. T., a 43-year-old white woman, was admitted to the Hartford Hospital with a three-month history of intermittent, dull, throbbing left neck pain and paresthesia in the left pre- and postauricular and left occipital areas occurring intermittently and lasting approximately thirty minutes. During the three or four days prior to admission, the symptoms increased in frequency and became refractory to medication. The history revealed an automobile accident eleven years prior to admission, with cervical neck strain. Physical examination disclosed a full range of neck motion with pain on left lateral flexion. No masses could be palpated, but there were tenderness along the left upper border of the trapezius muscle and questionable weakness of the left sternocleidomastoid muscle and left trapezius muscle. Hypalgesia and hypesthesia involved the left C-2 and C-3 dermatomes. On laboratory examination the hemogram, urinalysis, and cerebrospinal fluid protein were found to be normal. Radiographic studies included routine and laminagraphic evaluations of the cervical spine. A smooth area of erosion was discovered, which involved the posterolateral aspect of the fourth and fifth vertebral bodies, with enlargement of the left intervertebral foramen bounded by C-4 and C-5. The inferior aspect of the left fourth pedicle was also eroded. The defect had a sharp, sclerotic margin (Figs. 1 and 2). Findings were negative on cervical myelography (Fig. 3). Left vertebral arteriography via retrograde injection of the left brachial artery revealed no constriction or aneurysm of the vertebral artery. The vessel, however, was quite tortuous, unusually so in the midportion at the level of the fourth and fifth vertebral bodies. It looped medially at the lower margin of the fourth cervical vertebra, this loop corresponding to the bony defect observed on the routine and laminagraphic examinations of the cervical spine (Fig. 4). It was the opinion of the neurosurgical consultant that the symptomatology was not on the basis of this abnormality. Therefore, no specific therapy was instituted.