Conductive TiN/Si3N4 ceramic composites were processed by electrical discharge machining (EDM) and their microstructure and conductivity investigated. A low electrical resistivity of 1.25 X 10(-3) ohm.cm was obtained in 40vol%TiN/Si3N4 composite. The whole process of tool electrode wear is evaluated by sinker-EDM. The machined surfaces of TiN/Si3N4 ceramic composites were examined by scanning electron microscopy (SEM) and profilometry to determine the surface finish. Micropores of 700 mu m in depth and 70 mu m in in diameter were successfully machined in TiN/Si3N4 composites by the micro-EDM method.