Electrical discharge wire cutting (EDWC) is a spark erosion process used to produce complex two-and three dimensional shapes through electrically conductive workpieces. Newer and more exotic materials created and/or demanded by space technology sometimes cannot be economically cut using conventional cutting tools, but cut effectively by EDWC. The process wastes very little workpiece material due to its small kerf size, coupled with the fact that the process can accurately cut unusual shapes. In modern manufacturing industry, EDWC has been extensively used to machine complicated shapes on advanced materials with high accuracy. This paper presents the result of an experimental investigation on the machinability of A390 hypereutectic Al-Si alloy using wire electrical discharge machine. The effect of the modification and grain refinement treatments on the microstructure on the machining conditions was evaluated. The process parameters taken into consideration are the average gap voltage, surface finish type, pulse frequency, cutting speed, material removal rate, and kerf size.