In order to clarify the mixing effect of cation on the electrical conductivity and the hydration, the electrical conductivity of La0.9Sr0.1 (Yb1 - xMx)O3 - delta (M = In, Y) has been determined by the four-probe AC technique in the temperature range of 673-1173 K. The proton concentration was estimated from the change in weight due to hydration by a thermogravimetric analysis. The conductivity and proton concentration increased with the increase in the In3+ content on the Yb-site. On the other hand, the electrical conductivity and protonic concentration of La0.9Sr0.1(Yb1 - xYx)O3 - delta showed minimum values at x = 0.5. (C) 2013 Elsevier B.V. All rights reserved.