The Giacomini vein is present in 2.5%-10% of all patients having a phlebography because of varicosis. In a patient analysis of the last 5 years 129 patients were detected with a Giacomini vein (2.5%) out of a total of 5132 patients with varicosis. This vein was found in a significantly higher number of patients with a combined insufficiency of the long and short saphenous vein (p = 0.0001). An analysis of the different insufficiency patterns showed a Giacomini vein in 80% of insufficiency of grade I of the long and short saphenous vein. Likewise, this vein could be detected in more than half of the cases with complete insufficiency of both venous trunks (51%) as well as in 55% of the patients with a short saphenous vein insufficiency of grade III and an incomplete insufficiency of the long saphenous vein. On the other hand, there was no connection between insufficiency of the long saphenous vein, incomplete insufficiency of the short saphenous vein and the presence of the Giacomini vein. From these results we draw the conclusion that the Giacomini vein is a pathophysiologic connection between the two providing areas and thus transfers the insufficiency from one vascular system to the other. It hereby enhances the combined varicosis of both trunks as well as the formation of relapses. Therefore the Giacomini vein should always be stripped or removed by exeresis.