In recent years, the research work in material science has encouraged the development of advanced ceramic materials. Boron carbide has many applications in industries for manufacturing of products such as water jet nozzle and abrasive particles. In this paper several experimental tests have been conducted to study the effect of process parameters in machining of boron carbide "B4C" by using the electrical discharge machining process "EDM". The effect of voltage variation, current intensity, on-pulse and off-pulse durations on surface roughness (Ra) and Material Removal Rate (MRR) were studied simultaneously by utilizing the Design Of Experiment (DOE) technique. This research work indicated that the "EDM" process can be used to machine semi-conductor materials such as "B4C" successfully. In addition, it was found that, the quantity of material removal rate and the quality of workpart surface roughness could be affected by the variations of these process parameters. Finally, the experimental results obtained were compared with the published results reported by other scientist, and a good agreement was found between them. © 2014 Sharif University of Technology. All rights reserved.