Sixty menisci have been studied by scanning electron microscopy. In the frontal plane of the middle third of the meniscus, two distinct parts can be discerned - a central part corresponding to the medial two thirds and a peripheral part corresponding to the lateral third. Collagen fibres can be arranged in four different ways; radial fibres in the central portion; a marginal area underlying each surface of the meniscus made up of mixed collagen fibres; circumferential fibres in the peripheral part and a fascicular layer of fibres made up of loose connective tissue arising from the articular capsule and penetrating into the circumferential fibrous layer. The authors consider that the radial fibres are best adapted to pressure, whilst circumferential fibres are submitted to traction forces; the marginal areas are best adapted to gliding forces. Both menisci comprise a single functional unit.