Electric discharge machining is one of the widely used nontraditional methods in manufacturing industry. In the present study, the effects of discharge energy density on the material removal rate, electrode wear rate, surface average roughness of the workpiece and the tool electrode were investigated. AISI 1040 steel as workpiece material and electrolytic copper as tool electrode were selected. Experiments were designed and conducted using one-factor-at-a-time approach. During the experiments, current and voltage were kept constant, whereas pulse on time and pulse off time were varied at two levels. In order to investigate and analyze the effects of discharge energy density on the responses, different diameters of the tool electrode were used. It has been observed that the discharge energy density could be considered as a significant factor for appropriate selection of process parameters for better machining characteristics.