Impedance spectroscopy measurements were carried out on a series of PtAu and PtRh electrodes applied onto YSZ ceramic substrates. Impedance spectra were collected in the 10mHz-100 kHz frequency range using a three-electrode arrangement with either PtAu1 % or PtRh 20% as the working electrode, and Pt metal as reference and counter electrodes. Measurements were done at temperatures 550 and 750 degrees C in a range of atmospheres with oxygen contents varying from 0% to 21%. A short physical interpretation of observed phenomena was presented. The results seem to confirm that two different mechanisms of electrode reactions are employed in the Pt[YSZ system for lower temperature (550 degrees C) and higher temperature (750 degrees C). (c) 2007 Elsevier B.V. All rights reserved.