In the present investigation, a radically new and simple method of evaluation of the proton conductivity is proposed. This method is based on the conductivity measurement of ceramic materials depending on the oxygen partial pressure (pO(2)) at a gradual transition from the atmosphere of pure oxygen to one of wet hydrogen: O-2 -> O-2 (H2O) -> H2O (O-2) -> H2O -> H2O (H-2) -> H-2 (H2O). Experimental data of total conductivities for the solid electrolyte BaCe0.9Gd0.1O3-delta (BCG) have been fitted with modeling ones in accordance with the defect chemistry model at 600, 750 and 900 degrees C. Experimental and theoretical relationships correlate well with each other, demonstrating the success of the proposed model description. Analysis of dependences of the total conductivity as a function of pO(2) with simultaneous change of pO(2) and water partial pressure (pH(2)O) allows the estimation of the contribution of the partial conductivities (protonic, oxygen ionic, electronic) in the total one and the identification of the areas of purely ionic and purely protonic conductivity. Using the obtained data, some transport phenomena of proton-conducting materials, which were not previously interpreted, are discussed. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.