An electrochemical machining technique involves moving a cathode (2) towards an anodic workpiece (1). A current is passed through an electrolyte which flows between the cathode (2) and workpiece (1) so as to cause material to be removed electrolytically from the workpiece (1). A vibratory movement is imposed on the cathode (2) and the current passed between the cathode (2) and workpiece (1) is also varied. The vibratory movement may consist of a main sinusoidal oscillation and a secondary ultrasonic vibration, and the current variation is synchronized with the main vibration so that current pulses, and ultrasonic vibration pulses, coincide, with a predetermined small phase shift, with peaks of the main vibration corresponding to the smallest gap between the cathode (2) and workpiece (1).