A series of compounds La0.9Ca0.1Cr1-xNixO3 (x = 0.0-1.0) are synthesized by a wet chemical method. The crystal structure of La0.9Ca0.1Cr1-xNixO3 will become from an orthorhombic system (x < 0.7) to a hexagonal system (x > 0.8). The calculation for the valence orbital ionization energy (VOIP) of 3d electron of the Cr3+ and Ni3+ ion indicates the possible presence of the CO4+ ion in the compounds. The electric conductivity of the compound in air is measured over a temperature range from 293 to 1073 K, Arrhenius plot of ln(sigmaT) versus 1/T for La0.9Ca0.1Cr0.5Ni0.5O3 is composed of two line segments. The discontinuity at 465 K in Arrhenius plot may indicate the occurrence of the phase transformation in the compound. The crystal structure of La0.9Ca0.1Cr1-xNixO3 will vary not only with the content of the nickel ion, but also with temperature. (C) 2002 Elsevier Science B.V. All rights reserved.