METHODS This report illustrates two different cases of cervical pseudarthrosis in ankylosing spondylitis. OBJECTIVE To point out the extreme rarity of this condition at cervical level, to discuss the pathogenesis, and to stress the necessity of surgical management. BACKGROUND Pathogenesis of pseudarthrosis in ankylosing spondylitis is discussed. Several factors are involved: trauma, which may be major or minor and undetected; stress fracture; and inflammatory changes. Major trauma was the cause of pseudarthrosis in the first patient, whereas stress fracture and inflammatory changes were the probable causes in patient 2. In patient 1 there were signs and symptoms of cord compression. Patient 2 was referred because of functional disability resulting from kyphosis and because of potential neurologic risk. METHODS Cervical fusion was performed in both patients. Patient 1 underwent posterior fusion; patient 2 had combined fusion. Patient 1 also underwent a lamineotomy. RESULTS The course of the disorder after surgery was uneventful in both patients. Neurologic symptoms subsided in patient 1; kyphosis was corrected in patient 2. Both patients resumed their preoperative activities. Follow-up evaluation was done 6 years after surgery in patient 1 and 2 years after surgery in patient 2. CONCLUSIONS Pseudarthrosis of the cervical spine in ankylosing spondylitis is extremely rare. Presentation of the two patients was different in terms of pathogenesis and signs and symptoms. Surgical treatment is advocated for this disorder.