Several phlebotropic drugs, or edema-protecting drugs, are available, the most important of which are found in the gamma-benzopyrone family (flavonoids). gamma-Benzopyrones can be plant extracts, semisynthetic preparations, or synthetic preparations. This family is divided into two different groups: flavones and flavonols, and flavanes (flavanones). The flavone group contains various types of molecule and includes diosmin. Here we discuss the pharmacologic aspects in edema associated with chronic venous insufficiency (CVI) of one of the reference phlebotropic drugs, micronized purified flavonoid fraction (MPFF), a semisynthetic preparation from the diosmin group, which represents the latest improvement in flavonoid formulation. Before we detail the pharmacologic aspects, a brief summary of the pathophysiology of edema in CVI is necessary. Several factors are implicated: the veins, which create the conditions favorable to edema; the microcirculation, which is the site of fluid transfer into the interstitial tissue; and the lymphatics, which have a limited possibility to reduce edema. Major discoveries are currently being made in CVI and the microcirculation. Results of studies show that MPFF decreases capillary permeability and increases capillary resistance, which could partly be explained by inhibition of leukocyte activation, migration, and adhesion. This inhibition is linked to a significant decrease in plasma levels of endothelial adhesion molecules (VCAM-1 and ICAM-1) after MPFF treatment. Thus, the CVI-induced damage to the microcirculation is counteracted by MPFF. The lymphatic system is also improved by MPFF treatment. The lymphagogue activity of MPFF has been demonstrated in experimental animal models and confirmed by microlymphographic measurement in patients suffering from severe CVI. The pharmacologic activity of MPFF in lymphedema was observed in a study using an animal model of acute lymphedema and in a study in patients with upper limb lymphedema secondary to breast cancer treatment. All these findings point to the importance of acting on each factor involved in the formation and maintenance of edema. This pharmacologic activity is indeed reflected by the clinical efficacy on edema observed during treatment with MPFF.