An electrosurgery instrument having a radio frequency oscillator energized from a power supply controlled by a switching arrangement to produce either dc, full wave rectified ac, or half-wave rectified ac at its output, depending upon whether it is desired to operate in the cut, coagulate, or fulgurate modes, respectively. The level of output voltage of the power supply may be set to any value within a range and thereafter increased by a fixed percentage upon the operation of a remote control switch. The level of output voltage in any mode of operation, once set, is regulated by a feedback control circuit to minimize sparking at the electrode tip. The oscillator output is coupled to an operating probe through an impedance transformer and coaxial cable designed to deliver maximum radio frequency power to the patient without the use of a ground plate. An indicating lamp is connected to points of different potential in the cable and within the probe in order to give a positive indication of the presence of radio frequency power at the probe tip.