Under certain conditions the usual gas‐discharge circuit was found to give rise to relaxation oscillations. The relaxation oscillations produce a series of very narrow pulses with random pulse repetition interval, which appear as noise. The amount of noise was found to depend upon the gas, the cathode electrode material, the power supply voltage, and the external circuit configuration. It seems that this mechanism may be responsible for most of the high level noise usually reported from gas discharges. The pulsed nature of the apparently continuous discharge appears to be a fundamental property of the low‐current, cold‐cathode arc which has not been considered previously.