The invention relates to a device (10) for thermosurgery. The device (10) comprises a generator (12) for supplying high frequency electrical treatment energy, an interface connection arrangement (14) which permits the connection of a plurality of electrodes to be placed on or in the body of a patient (18), the electrodes comprising an application electrode (16) to be positioned in the area of the treatment site and a plurality of planar counter-electrodes (21, 22, 26, 27), and impedance measurement means (30, 35, 40) which permit impedance measurement in a plurality of measurement circuits, each of which passes via at least one counter-electrode (21, 22, 26, 27) connected to the interface connection arrangement (14).
