The flavonoids form a group of low molecular weight polyphenolic plant metabolites of which the average Western diet contains approximately 1 g/day, found in e.g. fruit, vegetables, tea, coffee, and wine [1,2]. Although the potent antioxidant properties of flavonoids are well recognized [2-9], they have not received as much attention as have vitamins C and E and beta-carotene. A series of biological functions have been demonstrated for different flavonoids. Thus these substances can scavenge free radicals [5], prevent lipid peroxidation [7], and inhibit low-density lipoprotein oxidation [4, 10]; they also possess anti-inflammatory actions [1] and inhibit enzymes such as cyclooxygenases, lipoxygenases, and phospholipase A 2 [6]. Also actions, related or not to the antioxidant properties, such as prevention of thrombosis [11], prevention of platelet activation [12], inhibition of plasminogen activator inhibitor-1 (PAI-1) production [13] or stimulation of endothelium-dependent relaxation [14] have been reported.A purified micronized flavonoid fraction (Daflon 500 mg) 1 was recently shown to have a beneficial effect on venous ulcer healing [15]. This flavonoid fraction, which consists of 90% diosmin and 10% hesperidin, is clinically used for the treatment of chronic venous insufficiency and hemorrhoidal attacks; its anti-edematous properties in man have previously been demonstrated [16]. Recent animal studies with Daflon 500 mg have revealed some of the mechanisms that could explain at least part of its clinical properties. Thus Daflon 1 Daflon 500 mg is also registered as Detralex, Capiven, Arvenum 500, Ardium, Alvenor, Variton and Venitol.