Pressurised operation of solid oxide fuel cells (SOFC) has been shown to significantly improve their performance (Singhal, 2000) [1], however little work has been done on the effects of pressure on SOFC cathodes. The effect of pressurised oxygen on the area specific polarisation resistance (ASRp) of (La0.8Sr0.2)(0.95)MnO3-delta/8YSZ SOFC cathodes was determined by electrochemical impedance spectroscopy (EIS). Pellets of 8YSZ were pressed and sintered at 1350 degrees C, and screen printed layers of LSM/8YSZ cathode and LSM current collector were applied and sintered at 1300 C and 1200 C respectively. EIS was carried out between 1 and 3 bar oxygen at 800-1000 degrees C. One process dominated the spectra, and was identified as process C, (Jorgensen and Morgensen, 2001) 12] by comparison of measured and reference frequency maxima, the dependence of polarisation resistance on P-o2, the capacitance, and the activation energy. It is suggested that this represents the physical process of dissociative adsorption of oxygen at the triple phase boundaries of the electrode. A second process, with a magnitude almost independent of P-O2, is observed, which may be process B [2], related to transport of oxygen ions in the YSZ. (C) 2010 Elsevier B.V. All rights reserved.