A striking feature of developing rabbit joints is the presence of a pericellular ring of type V collagen around the cells of the chondrogenous layers before cavitation and this persists around the articular chondrocytes throughtout life. To investigate whether type V collagen is found with a similar distribution in the articular cartilage of other species, equine and human articular cartilage was examined. A pericellular ring of type V collagen was found around the articular chondrocytes of both species in cartilage from young and old animals. Type Xl collagen is closely related to type V collagen and hybrid molecules of types V and Xl a-chains are known to exist. A significant feature of type V collagen is that it may be used as a marker of articular chondrocytes in a variety of mammalian species.