Intraoperative descending saphenography was performed in 20 legs (17 patients) with primary varicose veins to determine the sites of venous reflux (the sites of valve incompetence) in the great saphenous vein. By this phlebography, the sites of valve incompetence in the great saphenous trunk could be visualized when a pressure gradient was produced between deep and superficial venous systems by our manual compression technique. There were variations in the sites of truncal reflux; the retrograde flow of the contrast media was observed in the entire length of the great saphenous vein (type 1), normal portions were present in the trunk at the lower leg (type 2), or the trunk was normal at the thigh (type 3). In some cases, retrograde venous flow from the saphenous trunk entered once into variceal branches and further drained into the trunk passing some distance (3 legs). Type 2 and 3 accounted for 15 legs (75%), and selective stripping operation with preservation of the normal portion of the trunk was considered to be possible in these types. Since the length of the portion that could be preserved was 20.5±4.0cm (mean±SD) in type 2, and less than 15cm in 2 legs, use of the vein for arterial reconstruction seems to be limited.