Improvement of the polymer electrolyte fuel cell (PEFC) requires development of highly active electrodes of low cost to facilitate its widespread use. In the present study, the possibility of applying conventional activated carbon particles loaded with Pt to the electrode catalyst layer was tested because the particles were promising in dispersion of Pt and preparation cost. The catalyst layer was formed from the particles and Nafion(R) and was supported as a thin film on a rotating glassy carbon disk electrode (GC RDE). Activity for oxygen reduction was evaluated by the hydrodynamic voltammetry in perchloric acid to give a current free of the influence of mass transfer in the solution. Compared with a conventional catalyst layer formed from carbon black loaded with Pt, the new catalyst layer exhibited a significant, approximately 6-fold increase in current in the high potential region corresponding to a 100 mV increase in electrode potential. Activity, however, was retarded in the low potential region. This disadvantage was overcome by mixing a conductive agent into the layer and covering it with another layer containing carbon black loaded with Pt. This double catalyst layer exhibited increased activity across all potential regions, indicating the availability of the activated carbon in the electrodes. (C) 2003 Elsevier Science Ltd. All rights reserved.