Activated carbons were employed for the support material of catalyst, in the direct methanol fuel cell (DMFC). Until now, most of the papers related to the catalyst of fuel cells reported carbon blacks as catalyst support materials. In the present study, an activated carbon was re-activated by chemical activation method with NaOH at the various temperatures for the development of meso or/and macro pores. By using these pretreated activated carbons, Pt-Ru catalysts on the activated carbons (Pt-Ru/AC) which have various surface areas and porosities were prepared for the anode catalyst of DMFC. Surface areas and the crystal sizes of active metals were measured by N-2 adsorption and XRD, respectively. The performance of prepared Pt-Ru/AC catalysts has been evaluated by using the typical I-V curve of air breathing-type DMFC single cell. By this study, the optimum conditions of catalyst were suggested by correlating the catalyst reactivity with surface areas, pore sizes, metal sizes and distances between active metals. (C) 2002 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.