Electro-discharge machining removes metal with very short lived electric pulses between electrode and workpiece which are immersed in dielectric liquid. With limited feedback available to the operator, the process is very difficult to approach and maintain efficient machining performance. A systematic approach is taken here by applying incomplete process information for off-line process planning and by minicomputer technology for on line adaptive control. Off-line process planning determines the optimal current level and pulse duration for the roughing and finishing. By sensing down feed and pulse efficiency, on line adaptive control adjusts servo voltage and off time. Experimental investigations with two repetitions show that the system can complete the job with a shorter machining time by detecting and responding more efficiently to disturbances in the process than manual control.