The invention relates to an HF surgical instrument for treating, in particular for cutting and coagulating, biological tissue by means of an HF current. The HF surgical instrument comprises an HF generator for supplying an HF current to a cutting electrode and at least one control device for interrupting an HF current circuit. The control device comprises a current monitoring device, which detects the amplitude of the HF current and then generates a first switch-off signal when the HF current decreases over a defined period of time and/or the HF current falls below a threshold value characterizing a state of the treated tissue, as well as an arc monitoring device, which generates a second switch-off signal when an arc is formed between the cutting electrode and the tissue. The control device is configured in such a way that the HF current circuit is interrupted in response to the first switch-off signal or the second switch-off signal.
