This article reviews the mechanisms by which micronized purified flavonoid fraction (MPFF; Daflon 500 mg) acts on symptoms as well as on edema in patients with chronic venous disease, in the light of new advances in the understanding of the pathophysiology of this chronic condition. Deterioration of venous wall tone followed by valve dysfunction leading eventually to varicose veins are the key pathophysiologic features that produce venous hypertension. Both mechanical and biological factors are responsible for the deterioration of the venous wall in large veins. These are decreased shear stress and hypoxia of the media and of the endothelium, which act as triggering factors for biochemical reactions leading to inflammation. There is a body of evidence that inflammation in chronic venous insufficiency (CVI) plays a role right from the early stages of venous dysfunction and venous valve restructuring. The whole process of venous wall stretching and dilation is painful and may present as leg heaviness, a sensation of swelling, and paresthesia. Daflon 500 mg relieves symptoms, edema, and red blood cell aggregation, which cause paresthesia and restless legs. At the level of the microcirculation, dysfunction of microvessels is observed, characterized by an increase in capillary permeability followed by skin changes. The earliest manifestation of microcirculatory disorder is edema. At this level, Daflon 500 mg acts favorably on microcirculatory complications by normalizing the synthesis of prostaglandins and free radicals. It decreases bradykinin-induced microvascular leakage and inhibits leukocyte activation, trapping, and migration. Its efficacy in decreasing CVI edema and ankle swelling has been proven in rigorous studies that are reviewed in this paper. Daflon 500 mg, a well-established oral flavonoid that consists of 90% micronized diosmin and 10% flavonoids expressed as hesperidin, may be prescribed from the very beginning of the disease for the relief of pain and edema, and in any CVI patient presenting with symptoms as well. Daflon 500 mg is thus the first-line treatment for edema and symptoms of CVI at any stage of the disease. At advanced disease stages, Daflon 500 mg may be used in conjunction with sclerotherapy, surgery, and/or compression therapy or as an alternative treatment when other treatments are not indicated or not feasible.