The invention relates to an electrosurgical instrument and a method for puncturing a wall of a body lumen. The electrosurgical instrument includes an elongate applicator shank which is guided, in a mobile manner, in a guide catheter, a distal applicator electrode and a catheter electrode, arranged on the guide catheter and electrically insulated with respect to the applicator electrode. The method for puncturing a wall of a body lumen includes the steps of inserting a guide catheter, in which an elongate applicator shank is guided in a mobile manner, up to a wall of a body lumen, applying a radiofrequency AC voltage to a distal applicator electrode and a catheter electrode which is arranged on the guide catheter and electrically insulated with respect to the applicator electrode.
