A simple direct mixing of carbon-supported catalysts with Nation without adding any additional organic solvents was used to make electrodes for oxygen reduction in PEM fuel cells. For E-TEK 20% Pt/C, a Nation content of 30% in the catalyst layer exhibited the best performance. Electrode dried from 90 to 150 degreesC showed little difference in performance. Highest power densities increased almost linearly with cell temperature, and values of 0.52, 0.60, 0.63, and 0.72 W/cm(2) were achieved at 35, 50, 60, and 75 degreesC, respectively, for a cathode with a Pt loading of 0.12 mg/cm(2) and operated using air at ambient pressure. A maximum performance was achieved with Pt loadings of 0.20+/-0.05 and 0.35+/-0.05 mg/cm(2) for 20 and 40% Pt/C, respectively, while the maximum performance using 40% Pt/C was only slightly better than that using 20% Pt/C. A Nafion/carbon sublayer with up to 30% Nation content added between ELAT and the catalyst layer did not show any effect on performance.