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Stainless steel has been widely used in many medical fields , defence, chemical, construction, and aerospace due to its characteristics of good corrosion resistance, low thermal conductivity, and high strength at elevated temperatures [1]. Among other grades of stainless steels, AISI 304 SS is difficult to drill with conventional methods, and the electrical discharge drilling (EDD) process has recently been used for this purpose. EDD is an electro-thermal process used for drilling small holes on electrically conductive materials, based on the eroding effect of electric sparks occurring between the tool electrode and workpiece [2]. Drilling operations are conducted using tubular (hollow) electrodes through which dielectric fluid is flowing for washing removed particles (debris) away from the machining zone. Adequate flushing at interelectrode gap is significant in drilling holes with high aspect ratios. In such case, the proper circulation of dielectric and effective debris removal are difficult to achieve, which affect drilling performance and hole features. Numerous methods have been devised to improve flushing in EDD applications. Some researchers have tried to manipulate the relative movement between electrode and workpiece to stimulate debris removal. The orbital movement of the tool electrode in a radial direction was employed for manipulating the side interelectrode gap [3] and [4]. The bottom interelectrode gap was also manipulated by applying ultrasonic vibrations in the vertical direction [3], [5] and [6]. Moreover, it is reported that increasing electrode rotation [7] to [9] and dielectric pressure [10] to [12] have provided improvements in flushing and drilling performance. In contrast, only a few studies have been conducted for investigating the effect of electrode shape in the EDD process. Nastasi and Koshy [13] added geometric features of helical and radial slots on cylindrical copper electrodes to improve the gap flushing in drilling of 6061 aluminium alloy. Plaza et al. [14] studied the effects of helix angle and flute depth on helical electrodes to improve debris removal while increasing the hole depth in the drilling of Ti-6Al-4V. Another study on using helical electrodes with the implementation of ultrasonic vibrations on workpiece was conducted by Hung et al. [15] in the drilling of Hymu 80 nickel alloy. Comparative Experimental and Numerical Investigation on Electrical Discharge Drilling of AISI 304 using Circular and Elliptical Electrodes Bozdana, A.T. – Al-Kharkhi, N.K. Ali Tolga Bozdana1,* Nazar Kais Al-Kharkhi2 1 University of Gaziantep, Mechanical Engineering Department, Turkey 2 University of Baghdad, Automated Manufacturing Engineering, Iraq