We reviewed 40 extensive destructive vertebral lesions in 35 patients with established ankylosing spondylitis. Of these, 31 had presented with localised pain while three had a neurological deficit. The radiographs suggested ununited fractures through either ankylosed discs (37) or vertebral bodies (3). Corresponding fractures were seen in the posterior column in 34 cases. Sixteen patients with 18 lesions underwent anterior spinal fusion, and pseudarthrosis was consistently proven by histopathology. Two pseudarthroses healed in conservatively treated patients. Thirteen of the operated patients were followed for an average of 7 years 7 months. There were two cases of non-union and one required an additional posterior fusion; in the remainder fusion was sound.