An electrosurgical instrument is provided for cauterization and/or welding of tissue of varying impedance, thickness and vascularity especially in the performance of endoscopic procedures. The instrument compresses the tissue between one pole of a bipolar energy source located on one interfacing surface, and a second interfacing surface applying pressure in a predetermined range wherein one of the interfacing surfaces is positioned on an anvil with a specified preload and spring rate. A second pole is located one of the two interfacing surfaces. In a preferred embodiment, the second pole is located on the same interfacing surface as the first pole and an insulator electrically isolates the two poles. A preferred application of the invention is in a cutting instrument wherein a hemostatic line is formed along a cut line using RF energy.