The lower extremity venous system includes the superficial, deep, and perforating veins. The antegrade flow of blood within these veins is ensured by a system of muscular venous pumps and bicuspid valves. Dysfunction of the system may result from degeneration of the vein wall, post-thrombotic valvular damage, chronic venous obstruction, or dysfunction of the muscular pumps. Although chronic venous disease often receives less attention than arterial disease, it includes an array of manifestations resulting from a complex interaction of anatomy and hemodynamic failure. A thorough understanding of the highly variable venous anatomy is essential to understanding the underlying pathophysiology as well as in directing treatment.