An electrosurgical resecting instrument is provided having a resecting loop electrode on the distal end of a shaft and coupled to a high frequency voltage source. The loop electrode is configured to fit within a working end of a resectoscope (discussed below) and to remove small portions of tissue (e.g., chips of tissue). The loop electrode includes an active portion with a surface geometry configured to promote substantially high electric field intensities and associated current densities between the active portion and the target site when a high frequency voltage is applied to the electrode. The edges of the electrode are oriented substantially parallel to the shaft so that they will face the tissue as the electrode is moved axially in the cutting direction. This orientation facilitates formation of the vapor layer between the electrode edges and the tissue. The opposite or non-active side of the electrode may include an insulating layer to selectively reduce undesirable current flow from the non-active portion into tissue or surrounding electrically conducting liquids.