Spinal fusion for deformity of the cervical spine was done in thirty-three patients with rheumatoid arthritis. The average follow-up was three years. The deformities present were atlano-axial subluxation, superior migration of the odontoid process into the foramen magnum, and subaxial subluxation of the vertebral bodies. We devised a classification of the pain and the neural involvement in these patients and a new method of measuring superior migration. The surgical procedures for treating instability, intractable pain, or neural involvement, or a combination of the three, were: (1) a Gallie fusion of the first and second cervical vertebrae for atlanto-axial subluxation, (2) a fusion of the occiput and the second cervical vertebra for superior migration of the odontoid process, and (3) a posterior fusion for subaxial subluxation. The occiput was included in the fusion if superior migration of the odontoid process was demonstrated. The results show that four of five patients who had an anterior fusion had no improvement. Twenty-five patients had posterior fusion; in seventeen the condition was improved, in five there was improvement, and in three the condition was worse. Of nineteen patients with neural involvement, the condition was improved in eight, it was unchanged in seven, and it was made worse in two. There were three postoperative deaths and six additional unrelated deaths within two years of surgery. There were five pseudarthroses.