In this study, Taguchi's experimental design is used to determine the optimum component combination of a membrane electrode assembly and cathode current collector opening geometry to obtain maximum power density of an air-breathing polymer electrolyte membrane fuel cell at 0.5 V. An analysis of variance was conducted to figure out the optimum levels and significant differences of the effect of the combinations, followed by a performance measurement analysis. Experimental investigations of the effecting parameters enabled the determination of the optimum configuration of the MEA and cathode current collector opening geometry design parameters for maximum power density at a certain cell potential. Effective parameters which enable withdrawal of a maximum power output from an ABPEMFC at 0.5 V are, in order of effectiveness: the amount of platinum on the cathode, the thickness of the Nafion membrane, the cathode current collector opening geometry, and the amount of platinum on the anode. Optimum component combinations are: 0.45 mgPt cm(-2) for the platinum loading on the cathode, Nafion 112 for membrane, a vertical cathode opening geometry and 1.78 mg cm(-2) for the amount of platinum on the anode. For these component combinations, a 98.5 mW cm(-2) power output was obtained from an ABPEMFC at 0.5 V cell voltage.