Plasma current ramp‐up by lower‐hybrid waves in a high‐density regime (n¯e≳1×1019m−3) is investigated on the Alcator C tokamak [Nucl. Fusion25, 1127 (1985)]. A time‐averaged conversion efficiency (W˙−Pext)/Prfof over 15% has been obtained at a density ofn¯e&bartil;1×1019m−3, whereWis the poloidal field energy andPextis the external inductive power. The maximum conversion efficiency obtainable is lower at higher densities. Ramp‐up rates of over 1 MA/sec were obtained when rf current ramp‐up is applied to an Ohmically maintained plasma. Lower‐hybrid current drive can also be used to maintain the plasma while recharging the Ohmic‐heating transformer. The conversion efficiency of 10% obtained during recharging is found to be comparable to that obtained during ramp‐up under similar conditions.