Reactive arthritis, or Reiter's disease, characteristically affects the joints of the lower limbs in an asymmetrical pattern. Usually it does not affect the cervical spine, and atlantoaxial subluxations are the exception. This paper describes the case of an HLA-B27-positive female patient with a sexually acquired reactive arthritis where a non-reducible atlantoaxial subluxation was present. The patient was followed from age 27 to 41. By the age of 38, an anterior decompression of the cervico-medullary junction was performed by a transoral approach; in a second stage, the patient underwent an occipito-cervical posterior fusion. The pathological study revealed a non-specific and chronic inflammatory infiltrate.