Abstract: A method and apparatus for compensating for the wear of an electrode tool during machining by EDM of an electrode workpiece by the electrode tool. During penetration of the electrode tool into the electrode workpiece, relative displacement of the electrodes is stopped as soon as it reaches a predetermined reference position corresponding for example to a machining depth limit data entered in a control buffer memory. The reference position data is corrected as a function of the actual wear of the electrode tool which is measured by comparing the positions taken by the electrode tool when one of its active surfaces reaches the same reference position before and after a machining pass. The correction of the reference position data may be obtained either by successive approximations, or by a single calculation step effected after the first machining pass.