The effect of variations in flow rate and the humidity content of the cathode and anode gases on the performance of BaCe0.85Y0.15O3-delta electrolyte-based proton conducting ceramic fuel cell with ceramic composite cathodes are studied. Increased flow rate of gases has positive effect but the presence of humidity in the cathode/anode gases has negative effect on the performance. The effect of humidity is more pronounced when it is present in the cathode gas than when it is present in the anode gas. Also, the effect of humidity is dependent on the nature of the cathode material; in the case of La0.8Sr0.2MnO3-Gd0.1Ce0.9O1.95 cathode some of the reaction sites are occupied by H2O vapor and which leads to increase in the charge transfer resistance. Replacing La0.8Sr0.2MnO3-Gd0.1Ce0.9O1.95 with La0.8Sr0.2MnO3-BaCe0.85Y0.15O3-delta cathode leads to an increase in the effective area of three phase boundary, which mitigates the adverse effects of humidity to a certain extent. (C) 2013 Elsevier B.V. All rights reserved.