A medical instrument, in particular a generator for high-frequency surgery, comprises setting elements for presetting functions, and also functional elements for performing functions according to the settings. A controller interrogates the setting elements and controls the functional elements accordingly. Furthermore, a safety controller is provided for performing plausibility checks with the aid of information from the setting elements and also the functional elements, and for deactivating, or putting into a safe operating condition, the functional elements in the case of inadmissible working conditions.