In a series of 75 spines studied at autopsy, the authors found 21 (28%) affected by ankylosing hyperostosis. The 21 cases included three in the cervical spine, 12 in the thoracic spine, and five in the lumbar spine. One case had both thoracic and lumbar spine disease. The average age was 65 years (range, 50-90 years). The mean weight was 85 kg, which was 20 kg more than the mean weight of the nonaffected subjects. Four cases had adult onset diabetes mellitus. No other endocrine or arthritic disease was noted either clinically or at autopsy. No abnormalities of calcium or phosphorus metabolism were found. The cause of death was unrelated to their spine disease, and clinical records were devoid of any major complaints referable to the spine.