The kinetics of CO oxidation in excess hydrogen over a nanostructured Cu0.1Ce0.9O2-y catalyst prepared by a sol-gel method was studied under simulated preferential oxidation (PROX) reactor conditions. Reaction temperature was varied between 45 and 155 degreesC. The partial pressures of CO and O-2 in 0.5 bar excess of H-2 and He as a balance gas were varied between 0.001 and 0.025 and between 0.001 and 0.05 bar, respectively. The catalyst was found to be 100% selective in the temperature range from 45 to 90 degreesC. In this temperature range, the kinetics of the reaction was found to follow the redox mechanism represented by the Mars and van Krevelen type of rate equation. Kinetic parameters of the reaction calculated on the basis of this rate equation were found to be as follows: apparent activation energy for CO oxidation step, 57.2 kJ/mol, and for the catalyst reoxidation step, 60.2 kJ/mol. The observed reaction rate at the 0.01-bar CO partial pressure and stoichiometric O-2 partial pressure at 90 degreesC was 2.7 x 10(-6) mol/g(cat) s. The steady-state experimental data could be regressed almost equally well with the modified Langmuir-Hinshelwood model introduced by Liu et al. However, the transient experiments performed in our study reveal that lattice oxygen could be involved even at low reaction temperatures, thus favoring the use of a steady state Mars and van Krevelen kinetic model.