Hadfield steel, due to its high manganese content, is difficult to drill and work-hardens very quickly. In this study, Hadfield steel material was drilled with micro-size deep holes using the electrical discharge machining (EDM) technique, and hole diameter values were examined for specific machining parameters. Experiments were carried out with three different discharge currents (6, 12 and 24 A), three different electrode rotational speeds (200, 400 and 600 rev x min(-1)), three different pulse durations (12, 50 and 100 mu s), a fixed dielectric spray pressure (40 bars) and a fixed pulse interval (3 mu s). It was determined that the hole profiles obtained following the tests are directly related to the machining parameters, and that the resulting average overcut (AOC) and taper (Tp) values increased with discharge current, electrode rotational speed and pulse duration. Analysis of variance (ANOVA) conducted demonstrates that pulse duration is the dominant parameter affecting AOC, whereas pulse duration has the highest effect on Tp. When determination coefficients and normal probability plots were compared for the mathematical models obtained from analyses conducted for the prediction of test values, it was observed that the models obtained by quadratic regression analysis exhibited a better performance than the models produced by linear regression analysis.