The mechanical strength of connective tissues is dependent on the integrity of their fibrillar collagen frameworks. The objective of the present study was to assess type-II collagen damage (denaturation) in the adult human intervertebral disc compared with articular cartilage, in order to determine whether damage to this molecule may vary in different anatomical sites in the same person. A new immunochemical assay was used to measure the amounts of denatured and total type-II collagen in the annulus fibrosus and nucleus pulposus of the L5-S1 disc and in cartilage from the femoral condyles of the same individuals (n = 7). Denaturation of type-II collagen was significantly higher in both the annulus fibrosus and the nucleus pulposus than in articular cartilage. Such increased damage to type-II collagen in the adult disc may have relevance to the more pronounced degenerative changes observed in this tissue compared with articular cartilage.