The chemical composition has been determined in inner, middle and peripheral zones of 50 human knee joint menisci of ages 0–86 years. Of these, 12 showed areas of degeneration which were analysed separately. On a dry weight basis, normal adult tissues contained 77.9 ± 0.4% collagen, 8.1 ± 0.8% non-collagenous proteins (NCP) and 1.0 ± 0.1 % hexosamine. With aging, the level of collagen increases and NCP declines. In degenerate areas, a statistically significant loss in collagen, and rise in NCP and hexosamines was observed, relative to normal menisci of the same