The oxygen reduction reaction (ORR) was studied in 0.5, 1.0 and 2.0 M sulfuric acid solutions on locally developed carbon-cloth-supported gas diffusion electrodes with the catalyst layers containing constant platinum loadings (0.4 mg Pt cm(-2)) but different platinum-to-carbon ratios and different PTFE contents. Cyclic voltammetry, steady state polarization curves, and the impedance method applied at several electrode potentials were employed in the experimental investigations.