Preparation of catalyst layer in PEMFC electrodes was investigated. Toray carbon paper was used as diffusion layer, and Johnson-Matthey 20% Pt/C was employed as catalyst. Electrode contains neither PTFE nor carbon powder. The optimal catalyst layer composition was discovered by orthogonal test method, with the use of cell voltage-current curve and cyclic voltammogram curve. The optimal amount of the Nation (ionomer) in the catalyst layer was found to be 1.4 mg/cm(2) when Pt loading was kept at 0.4 mg/cm(2). Power density of PEMFC achieved 0.37 W/cm(2) with air and H-2 were used at the outlet pressure of 0. 1 MPa. (C) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.