Aluminium alloys are conventional materials widely used in aviation, marine, automobile and electrical equipment. Aluminium alloy materials are relatively low cost, light weight and can be easily machined by both traditional and non-traditional machining processes. Aluminium Metal Matrix Composites (AMMCs), have been making inroads into various engineering applications where there are demands for strength and stiffness higher than those offered by the conventional aluminium alloys. Traditional machining of AMMCs, however, is challenging as their hard reinforcement tends to wrap around the conventional tool bit that leads to tool breakage. To address this problem, Electro-Discharge Machining (EDM) is being considered as a viable alternative to conventional machining. Key input process parameters of EDM such as the peak current, the pulse duration (ON-time) and pause duration (OFF-time) are varied to study their influences on the surface finish. The quality of the surface finish is indicated by the surface Roughness (Ra) and surface morphology of the metal surface. The effects of these parameters on the surface finish quality of alumina (A1203) particle-reinforced AMMC are then compared with those of an aluminium alloy. Performance of EDM machining on AMMC shows satisfactory result in surface roughness at low peak current, short ON-time and longer OFF-time. Response surface methodology is used to analyze and generate the mathematical model of output response. © 2012 Asian Network for Scientific Information.