As a fundamental study of the electrode performance of a direct methanol fuel cell (DMFC, DMFCs with different loadings of anode catalyst were prepared and operated with liquid methanol under various conditions at atmospheric pressure. The DMFC employed Nafion 112 as a solid polymer electrolyte and Pt-Ru/C and Pt/C catalysts for the anode and cathode, respectively. The effects of the Pt-Ru loading for anode and, using the cell with an optimum Pt-Ru loading, the temperature and feed rates of the oxidant gas on the cell performance were investigated. The cell performance was analyzed based on the measurement of the current-voltage characteristics and electrode impedance. The performance increased with the increasing Pt-Ru loading up to a certain amount. Over this value, the current density at a low cell voltage decreased with its increase resulting in the reduction of the power density. An unstable and temporal decline in the performance was observed near the vaporization temperature of the feeding liquid and at low feed rate of oxidant gas. It was considered that the mass transfer of the materials related to the electrode reaction was limiting at these conditions. The relatively large power density of 0.12 W/cm(2) was obtained with the optimum Pt-Ru loadings at 363 K under atmospheric pressure. (C) 2003 Elsevier Science B.V. All rights reserved.