An electrosurgical 
cutting blade (1) comprises a first 
electrode (2), a second 
electrode (3), and an electrical insulator (4) separating the first and second electrodes. The first and second electrodes have dissimilar characteristics (cross-sectional area, 
thermal conductivity etc.) such that the first 
electrode (2) is encouraged to become an 
active electrode and the second electrode (3) is encouraged to become a return electrode. The spacing between the first and second electrodes (between 0.25 mm and 3.0 mm) and the peak 
voltage supplied to the electrodes (2 and 3) are both selected such that arcing does not occur directly between the electrodes, but between the first electrode and the tissue at the 
target site. The arrangement is such that, in use, a thermal differential of at least 50° C. is established between the first and second electrodes (2 and 3), such that the second electrode is maintained below a temperature of 70° C. This is achieved either by thermally insulating the second electrode from the first electrode, and / or by transferring heat away from the second electrode, e.g. by conduction, forced cooling, or by means of a 
heat pipe (27).