The significance of perforating vein incompetence in patients with primary varicosis and the frequency of detection of perforating vein reflux need clarification. To develop a method for radionuclide visualization of venous blood flow and to evaluate the functional capacity of perforating veins. Forty eight patients presenting with disturbances in the greater saphenous vein basin (CEAP clinical classes C2-C5). All of them were examined by ultrasound scanning and radionuclide phlebography of the limb scheduled for surgery. Radiophlebography was performed by a modified technique using a pneumatic cuff instead of an ankle tourniquet to direct the total amount of the isotope into deep veins. Compression of the lower leg soft tissues with the cuff prevented washout of the radionuclide from the injection site in the proximal direction through subcutaneous veins; thereafter, toe movements ensured the uniform bolus distribution (through valveless perforating veins) in the remaining foot veins. After cuff deflation, the patients were asked to make ankle flexion-extension movements. A gamma-chamber was used to monitor the unobstructed transport of the radioisotope. In 37 (77%) patients, the radionuclide was evacuated only through the deep veins. No derivative circulation was documented. The retrograde filling of the greater saphenous vein with the radioisotope occurred within 20-40 seconds after the injection. Only then, it penetrated into the perforating veins through which the blood went naturally from subcutaneous to deep veins to again enter the antegrade flow. Thus, the perforating veins (even if incompetent) continued to perform their draining function. Radiophlebography with the use of a pneumatic cuff makes it possible to evaluate natural blood flow under conditions maximally close to the physiological ones. The majority of the patients presenting with primary varicosis do not exhibit perforating vein reflux. The perforating veins considered incompetent based on the results of ultrasound scanning continue to maintain the natural direction of the blood flow.