The electrical properties of acceptor-doped Cal(1-x)Zr(0.99)M(0.01)O(3-delta) (M=Mg2+, In3+) systems were investigated as a function of cation nonstoichiometry (0 <= x <= 0.05). The characterization was carried out using the impedance spectroscopy between 550 degrees C and 1100 degrees C in dry air. The contributions of the grain and grain boundary conductivity to the total conductivity were obtained from the impedance data. When the Ca deficiency (x) increased, the total conductivity rapidly decreased with the corresponding increase in activation energy. Although the grain conductivity increased slightly with increasing x, the total conductivity is mostly determined by the highly resistive grain boundary. With varying x, the activation energy of total conductivity showed the percolation behavior. The percolation threshold values vary according to the doped species. It may be due to the difference in concentration of oxygen vacancies of the specimens. (c) 2006 Elsevier B.V. All rights reserved.