Histological secitons of relaxed porcine aortic valves were studied from a mechanical point of view. The observations are combined into a tractable scheme of the tissue structure of the aortic valve. The valve leaflets can be regarded as an elastic meshwork, reinforced with stiff collagen bundles, showing an arrangement in one particular direction. The sinus walls consist of smooth muscle tissue, embedded in an elastic meshwork. The line of attachment of the leaflets to the sinus walls is constituted by the aortic ring, a crownlike fibrocartilaginous structure, containing large amounts of collagen fibres. This simple scheme of the tissue structure can be expected to provide important starting-points for both the interpretation of experimental results and the theoretical modelling of aortic valve mechanics and kinematics.