Anode supported solid oxide fuel cells have been tested and the degradation over time was monitored and analyzed by impedance spectroscopy. Reproducibility of initial cathode, anode and electrolyte performance was obtained. Anode (Ni/YSZ) degradation was analyzed for tests applying p(H2O) of 0.2 atm, 0.4 atm and 0.6 atm at 750 degrees C and 0.75 A/cm(2). The anode degradation could be well described by the equation: R-Ni,R-TPB(t)= R-Ni,R-0 + Delta R (1 - exp(-t/tau)). The initial resistance and total increase for the Ni-YSZ charge transfer resistance, R-Ni,R-0 and Delta R, were similar for all tests (i.e. not directly correlated with p(H2O)), but the characteristic time, tau, for the anode degradation was significantly higher for the test at p(H2O) = 0.2 atm than at p(H2O) of 0.4 atm and 0.6 atm. (C) 2010 Elsevier B.V. All rights reserved.