The age-related changes in glycosaminoglycan composition of human intervertebral discs were studied. Large number of tissue samples taken from 301 individuals at autopsy or at operation of prolapsed discs was investigated. It was found that the ageing process is accompanied by a progressive decrease in GAG content, both in annulus fibrosus and in nucleus pulposus. The GAG: collagen ratio significantly decreases. The KS and Ch-6-S were found to be the most abundant GAGs in both parts of the disc and their amounts decrease during the ageing. A distinct, age-related increase in KS:Ch-S and Ch-6-S:Ch-4-S ratios was observed. Significant quantitative differences between the GAG contents in normal and prolapsed discs were found. The nuclei pulposi of prolapsed discs contained less GAGs, especially KS and Ch-6-S in comparison to normal tissue of the same age. Furthermore, the age-related decline of GAGs:collagen ratio was more distinct in the prolapsed discs. It seems that these differences in GAG composition may be important in the mechanism of predisposition to discs prolapse.