Described are devices, methods and systems useful for achieving occlusion of vascular vessels. Percutaneous procedures can be used to occlude and obliterate the greater saphenous vein, for example in the treatment of varicose vein condition caused by venous reflux. Certain embodiments encompass the percutaneous delivery of an occlusion device inverted within a cannula, its deployment and filling, so as to occlude or obliterate a portion of a vascular vessel.