In the surgical treatment of varicose veins, it is very important to localize the place where the insufficient perforating vein &dquo;blows out&dquo; the blood from the profound veins to the superficial ones.The different procedures of Trendelenburg,1 Schwartz,2 Perthes,3 Marhorner and Ochsner,4 Pratt,5 Myers6 and others are, in our opinion, useful, but are not sufficient, and on occasions do confuse the clinical decision.Since 1952, we have been doing a very special clinical procedure, which we created, and we have found it unnecessary to use the other systems and phlebographies.The procedure is as follows: With the patient standing up, and the varicose veins visible, the examiner places his two thumbs firmly over any particular portion of a varicose vein pattern. One of the thumbs remains in a fixed position and the other one slides along the vein, firmly squeezing it, until it passes the probable insufficient perforating vein place; immediately, the emptied part of the varicose vein fills up from the sliding thumb position toward the fixed thumb place. That means that one insufficient perforating vein will have been passed at the precise moment.We repeat this procedure to make sure of the &dquo;blow out&dquo; place, and we mark it on the skin with a small circle. We have now finished investigating the first insufficient perforating vein.To find the second insufficient perforating vein place, we put the fixed thumb firmly over the circle of the first insufficient perforating vein place, just found. The sliding thumb starts moving from the side of the former, squeezing the visible vein, and at the moment the intermediate portion of the emptied vein between the two thumbs in a retrograde manner fills up, the place of the second insufficient perforating vein is found.We can repeat the procedure if necessary, to be sure of marking the second insufficient perforating vein place.For the other portions of varicose vein patterns, we follow the same procedure, marking all insufficient perforating veins we find.My research has proved this to be a simple procedure to follow and to interpret.When the insufficient perforating vein is not connected to the superficial vein, then a venous s.c. pouch will be formed, and palpation alone can localize it.On the other hand, if there are edema, dermatosclerosis or ulcers, the varicose