Duplex scanning of the subcutaneous, deep and perforating veins was performed to examine venous return and to establish the diagnosis of valvular venous insufficiency of the lower extremities in 32 clinically healthy subjects (64 extremities) and 38 patients suffering from varicose disease (VD), when the patient was in the horizontal and vertical position. It has been established that in VD patients, the diameter of the deep and subcutaneous veins is greater than that in healthy subjects. When the patient is in the vertical position, the venous lumen expands 1.5-fold on the average (1.6-fold in healthy subjects and 1.4-fold in VD patients) under the influence of orthoshtatic venous pressure (,the sum of hydrodynamic and hydrostatic pressure). The growth of the total venous pressure up to the design values in the distal segments of the lower extremities is removed not only by musculovenous pump (MVP) motion but also by the MVP of free standing (maintenance of body balance) as well as by the action of the arteriovenous pump (AVP). The frequency of recording the retrograde blood runoff at functional exerelse in healthy subjects when they are in the orthostatic position is dramatically reduced. This phenomenon may be related to the orthostatic dilatation of the great veins and tension of the cusps of the unchanged valves, which should be regarded as a functional component of the closing mechanism of the MVP, In YD patients when they are in the orthostatic position, the frequency of revealing the design valvular insufficiency (according to the duration of retrograde runoff) decreases in the deep and rises in the subcutaneous veins. Valvular insufficiency of the perforating veins of the leg was primarily recorded in the veins of Cockett. The data obtained indicate that examination of venous function of the lower extremities is desirable when the patients are in both horizontal and vertical position.