1. Human articular cartilage from normal femoral heads and from cases of osteoarthrosis in subjects of various ages has been examined histologically and by electron microscopy.

2. In specimens from middle-aged and old subjects, peculiar "matrix-streaks" have been observed in the deep zone of the pressure areas as oblique bands extending from the pericellubar halos into the adjacent matrix.

3. Ultrastructurally the streaks are correlated with an undulating pattern of the radially oriented collagen fibres.

4. The streaks are considered to result from a focal lack of acid mucopolysaccharide and from natural forces on the articular cartilage. Their appearance is assumed to be an early sign of cartilage disintegration associated with ageing.