Careful pathological examination of lumbar spines removed at autopsy has shown that degenerative changes are present in the intervertebral discs of all subjects by middle age. The degenerative changes are more marked and occur at an earlier age when evidence of vertical or posterior disc prolapse is also present. Degenerative changes in the discs are always accompanied by osteophyte formation on the margins of the vertebral bodies and remodelling changes in the apophyseal joints. There is a direct relationship between the degree of disc degeneration, marginal osteophyte formation on vertebral bodies, and apophyseal joint changes, which suggests that disc degeneration is the primary event leading to the clinical condition of 'degenerative spondylosis'.