Median nerve somatosensory-evoked potential (SEP) examinations were performed in 24 consecutive patients with rheumatoid arthritis who had symptomatic cervical spine instability. Eighteen patients had C1-C2 instability: in ten, the subluxation was completely reducible, and in eight, the subluxation was irreducible, with or without superior migration of the odontoid process. Four patients had superior migration alone, and two had subaxial subluxation alone. Abnormal SEPs were found in seven patients overall. However, 58% of those patients with irreducible atlanto-axial subluxation and/or superior migration of the dens demonstrated abnormal cervical cord conduction latencies. Patients with these radiographic findings may be at a higher risk for the development of overt myelopathy.