Five patients with ankylosing spondylitis who suffered severe neurologic complications after fracture of the cervical spine are presented. All developed delayed neurologic complications, ranging from 2 to 35 days after the initial injury (mean, 15.8 days). The diagnosis was delayed in four, and in three this delay contributed to morbidity. All fractures occurred in the lower cervical spine (C5 to C7). In three patients, the fracture was the result of minor trauma. A high index of suspicion, an appreciation of the extreme instability of these fractures, and prompt rigid immobilization with a halo vest or cast in the alignment of preexisting kyphosis are all important factors in preventing neurologic complications.