An account is given of the appearance of some low voltage, hot-cathode discharges generating high-frequency oscillations internally in gas at a pressure of the order of 10^-3 mm of mercury. The primary electrons are deviated laterally, as well as being accelerated or retarded in their longitudinal motion, at a distance of a few millimetres from the cathode, in or close to a layer of ionized gas which is brighter than the neighbouring plasma. The position of this layer changes discontinuously when a probe is moved through it, giving rise to an apparent abrupt alteration of the electrical properties of the discharge along a line normal to the cathode which is partly spurious. The layer becomes unstable if large currents are passed, and the tube then also generates oscillations with frequencies below 1 Mc/s. The discharge can be stabilized to higher currents by a longitudinal magnetic field. Two other instances are recorded of a close association of high-frequency and low-frequency oscillations.