IT has been suggested1 that fibrillation, the earliest change in osteoarthritic cartilage visible to the naked eye, may be the result of fatigue failure. Abnormally high stresses in the superficial layer of cartilage could be produced by unusually high applied loads, incongruity of the joint surface, or softening of the cartilage by mucopolysaccharide loss. Repeated cyclic loading could then lead to fatigue failure in the surface layer. To test this hypothesis postmortem human articular cartilage was subjected to repetitive compressive loads.