Metal-matrix composites (MMCs) have been increasingly used in automotive and aerospace industries because of their superior properties compared to unreinforced alloys. These materials are difficult-to-machine by conventional machining methods because of the hard and abrasive reinforced particles. The present work investigates the effect of voltage, electrolyte concentration and feed rate on radial over cut in electrochemical drilling of Al/B 4 C p metal matrix composites. Experiments have been conducted on electrochemical machine according to the principles of Taguchi's design of experiments method. Regression analysis was employed to develop mathematical model for radial over cut. Adequacy of the developed mathematical model has been tested using analysis of variance. Effect of machining parameters and their interactions were studied through the contour plots.