Electron microprobe analysis for the surface deposition and diffusion of tool material was carried out on mild steel (MS), high-carbon steel (HCS) and high-speed steel (HSS) work samples, machined by an electrical discharge process using a relaxation circuit in distilled water and kerosene at 225 and 56·25 mJ pulse energy, with copper and brass as tools. It was observed that high-energy machining results in lower surface deposition but more depth of diffusion. MS-HCS-HSS showed increasing surface deposition but decreasing depth of diffusion in the same order. Machining in distilled water at high-pulse energy resulted in lower surface deposition and depth of diffusion as compared to machining in kerosene. At low-pulse energy kerosene showed similar results.