The paper presents results of experimental investigations on the durability of tool-electrodes at the surface processing by pulsed electrical discharge in the gaseous environment. In order to increase the durability of the tool-electrodes by applying pulsed electrical discharge machining (PEDM) in the liquid and gaseous environments it is proposed to construct the tool-electrodes of materials resistant to electroerosion process. The electroerosion of the cathode mass at the processing of metal surfaces by applying PEDM in gaseous environment (air at normal pressure) depends parabolic on the charge voltage of the capacitor battery of the impulse. Investigations of mass erosion of the tool-electrode made of different materials have shown that the minimal erosion of metal surfaces at PEDM has stainless steel, followed by copper and tungsten, therefore it is proposed to construct the tool-electrodes of stainless steel for the used technological process