Spinal osteochondrosis, previously known as Scheuermann's disease and spinal osteochondritis, is common and is probably becoming increasingly prevalent. Its incidence in patients whose primary complaint was of backache was shown to be twice as great as that in the general population. There was also a significantly higher incidence of lower lumbar spondylosis in patients with previous osteochondrosis compared with those without. Osteochondrosis is thereby shown to be an important aetiological factor in spondylosis.