Abstract: The application apparatus according to the invention for applying a high frequency current for thermal sclerosis of body tissue, includes an electrode array (7) with at least three active electrodes (1-6) which are electrically conductingly connected to the body tissue, a high frequency generator (17) which can be individually electrically connected to the active electrodes (1-6) for producing a high frequency voltage, and a measuring device (13) for measuring the impedance of the tissue between the active electrodes (1-6). In addition the application apparatus includes a selector device (15) for selecting a sub-array (19) including at least two active electrodes (5, 6) from the electrode array (7), the selection being effected on the basis of the measured impedance.