In their paper on opossum cartilage, Archer et al. (1996) contend that their ‘data pose questions [ctdot ] to the idea that global patterns of matrix components exist in mammalian articular cartilages’. We believe that this statement is not supported by their data. The points at issue concern the distributions of chondroitin sulphate (CS) and keratan sulphate (KS) in adult cartilage. Earlier work showed that: (1) the highest concentrations of CS are in the midzone of the noncalcified layer of the cartilage (Stockwell & Scott, 1967; Maroudas et al. 1969; Lemperg et al. 1974), while the authors' opossum data apparently show that the intensity of staining with Safranin O (and various antibodies specific for CS) ‘is greatest in the upper third of the tissue depth’; (2) in the noncalcified cartilage, the concentration of KS increases with distance from the articular surface (Stockwell & Scott, 1967; Maroudas et al. 1969; Venn, 1978). By contrast in the opossum, the authors state that there was ‘intense labelling throughout the upper half of the articular cartilage depth’. They considered that this finding, in particular, questions ‘the notions which link KS substitution with conditions of low oxygen tension’, since articular cartilage generally obtains its nutrient and O2 through the articular surface and thence by diffusion through the tissue depth.