An optimal preparation method of electrodes has been sought to improve the performance of direct methanol fuel cell (DMFC). The electrodes were prepared with solvents of various polarities in catalyst ink and their single-cell performances were evaluated. A new equivalent circuit of methanol oxidation in DMFC anode has been introduced to find the origin of the difference in the anode performances. The performance of a single cell was high when less polar solvent was employed in catalyst ink. This has been attributed to the decrease in solubility of the ionomer (proton conductor) leading to the formation of a larger agglomerate with catalyst. Consequently, improved proton paths could decrease the pore electrolyte resistance in the catalyst layer. In addition, the secondary pores between those agglomerates became larger to make mass transfer process more facile. (C) 2004 Elsevier B.V. All rights reserved.