In this study, a new system for drilling deep micro-holes was designed for Hadfield steel (which is difficult to process with classical methods) with the electro-discharge-machining method (EDM) and the system was experimentally examined. The tests were carried out at three different discharge currents (6, 12 and 24) A, three different electrode-tool rotational speeds (200, 400 and 600) r/min, three different dielectric spray pressures (40, 80 and 120) bar, a constant pulse duration (12 mu s) and a constant pulse interval (3 mu s). After the tests the effects of the processing parameters on the basic performance outputs (the material removal rate -MRR), the electrode wear rate (EWR) and the relative wear (RW)) were investigated. Additionally, an analysis of variance (ANOVA) was also applied to identify the most significant factor. Optimum operating parameters were determined using the desirability-function analysis through the response surface methodology (RSM). It was found that the most effective variable affecting the MRR, EWR and RW was the discharge current. The discharge current was found to be the most significant control factor influencing the performance of the machining process.