Methane steam reforming and dry methane conversion over ceria, and ceria doped with 1.4 and 5% Nb cation has been investigated at 900 degreesC (a typical solid oxide fuel cell temperature). The influence of the calcination atmosphere on the Nb-doped ceria has also been studied. Use of reducing conditions leads to significantly lower crystallite size, higher specific surface area and greater Nb solubility. Nb-doping lowers activity mainly as a consequence of strong segregation of Nb to the ceria surface. Kinetics of steam reforming are interpreted in terms of a redox mechanism.