Although great advances have been made in the operative treatment of vascular disorders, the management of most venous problems is still nonsurgical. Daflon 500 mg* is a micronized flavonoid mixture of 90% diosmin and 10% hesperidin that has phlebotonic properties. The efficacy of Daflon 500 mg has been investigated in three double-blind, randomized trials using strain gauge plethysmography to provide quantitative information on venous hemodynamics in patients with chronic venous insufficiency. In total, 183 patients were treated with Daflon 500 mg versus a control group of equal number of patients. Daflon 500 mg produced a significant decrease in venous capacitance, venous distensibility, and venous emptying time (P < 0.001). In addition, these changes were accompanied by improvement in clinical symptoms and a decrease in the supramalleolar circumference. Clinical side effects were rare and led to treatment withdrawal in only 3 patients. It is concluded that Daflon 500 mg is of benefit to patients with chronic venous insufficiency.