The aetiology of varicosis is still unclear. Investigation of changes in normal veins which result in the formation of varicosis led to examination of elastic properties and histomorphological alterations in the region of the extracellular matrix in the vessel wall of the long saphenous vein in normal and varicose veins. The rigidity of varicose veins was higher than that of normal veins; there was no difference between the varicose vein above a competent valve and the "normal" vein below this competent valve. The matrix proteins demonstrated an increase in total fibres, whereas the elastic fibres were reduced and fragmented, explained the rigidity of varices. These results suggest that the role of the venous valves in the development of varicose veins is secondary to changes of the vein wall.