By application of electron cyclotron heating (ECH) to the WT-2 tokamak, the high-frequency instability (relaxation oscillation) excited by the lower-hybrid-wave-driven current is suppressed and the loop voltage decreases without voltage spikes, implying that the driven current increases. This suppression can be ascribed to the isotropization of the current-carrying beam electrons by ECH. © 1983 IOP Publishing Ltd.