A catheter delivers an electrode within a vein for a minimally invasive treatment of varicose veins and venous insufficiency using RF energy. The catheter is introduced into a patient and positioned within the section of the vein to be treated. The electrode radiates high frequency energy towards the vein, and the surrounding venous tissue becomes heated and begins to shrink. The catheter includes a controllable member for limiting the amount of shrinkage of the vein to the diameter of the member. The electrode remains active until there has been sufficient shrinkage of the vein. The extent of shrinkage of the vein may be detected by fluoroscopy. After treating one section of the vein, the catheter and the electrode can be repositioned intraluminally within the vein to treat different sections of the vein until all desired venous sections and valves are repaired and rendered functionally competent.