In progressive rheumatoid arthritis (RA), arthritic affection of the upper cervical spine is relatively common, mainly manifesting atlanto-axial subluxation (AAS). However, posterior AAS (PAAS) is a very rare condition. We reviewed five RA patients with PAAS. All of the patients were aged women with progressive RA, who had been treated with steroids and had been hospitalized for many years. Two patients had symptoms of myelopathy due to spinal cord compression, and another one suffered from severe pain in the neck. These three cases were treated surgically with posterior atlanto-axial fusion or posterior occipito-cervical fusion, and the result was good. Conservative treatment has been indicated for the other two patients with only instability as indicated by stress X-ray. X-ray examination confirmed that the most remarkable finding was PAAS due to destruction or disappearance of the odontoid process. The more severely the odontoid process was eroded, the more backward the atlas was dislocated.