A gas laser having a circular cross-section at right angles to the direction of the beam propagation and having an optical resonator. For continuous or modulated continuous beam operation, the laser has a metal tube as an inner conductor which is connected to a radio-frequency voltage source. The outer conductor consists of a tube of electrically highly conductive metal which is arranged coaxially with respect to the inner conductor. Leaving an intermediate space, the inner conductor is sheathed by a jacket tube of dielectric material. An electrically highly insulating dielectric cooling fluid with a low loss factor for radio-frequency fields flows through the intermediate space between the inner conductor and jacket tube.
