Ru-added Ni catalysts supported on Al2O3 or MgAl2O4 were prepared and tested for the methane steam reforming to investigate the Ru-induced effects on the catalytic activity, the suppression of carbon deposition and the in situ self-activation of the oxidized catalysts during the reforming. The Ni catalysts promoted with a small amount of Ru (<= 1 wt%) showed a moderate reforming activity without a pre-reduction treatment using H-2; however, the Ni catalysts unpromoted with Ru were active only after reducing the catalysts with H2. Among the Ru-added Ni catalysts, the catalyst prepared by sequentially impregnating Ru by 0.5 wt% over the calcined sample of 20 wt% Ni/Al2O3 showed higher reforming activity than the catalyst prepared by the co-impregnation of 0.5% Ru and 20% Ni over Al2O3. It was also revealed that the Ru doping greatly suppressed carbon growth on the Ni/Al2O3 catalysts. Between the two support materials, MgAl2O4-supported catalysts were more active than Al2O3-supported catalysts. Most of the Ni on the MgAl2O4 support were finely dispersed NiO clusters, while the Ni on the Al2O3 support was hard-to-reduce NiAl2O4. The presence of Ru in a highly dispersed state appears to facilitate the reduction of such Ni-oxides and to decrease the coking propensity of the catalyst in the steam reforming of CH4. (c) 2006 Published by Elsevier B.V.