This article discusses four subsystems of the electrochemical machining (ECM) system: power source, electrolyte cleaning and supply system, tool and tool-feed system, and workpiece and workpiece-holding system. It describes the theory of ECM and provides information on the electrolytes used in ECM. The article reviews the methods associated with workpiece shape prediction. The procedures and integrated approach for the tool design in ECM are discussed. The article also explains the process control, capabilities, and the limitations of ECM. It concludes with information on the applications of ECM.