The thermal diffusivities of near-stoichiometric (U, Ce)O-2 solid solutions containing CeO2 up to 22 mol% were investigated in the temperature range of 298-1273 K using the laser flash method. Also, linear thermal expansion measurements were performed in the temperature range of 298-1673 K using a thermomechanical analysis. The thermal conductivities were determined by a calculation of the thermal diffusivity, the density and the specific heat. The thermal conductivities of the tested samples could be expressed as a function of the temperature by the phonon conduction equation k = (A + BT)(-1). The thermal conductivity decreased gradually with an increasing Ce content. This was attributable to the increasing lattice defect thermal resistance caused by the U4+, Ce4+ and O2- ions as phonon scattering centers. (C) 2005 Elsevier B.V. All rights reserved.