Water-gas-shift reactions over Pt-Re/TiO2 and Pd-Re/TiO2 catalysts were studied, using the closed gas circulation system and the fixed-bed flow-type reactor. The activity of Pd-Re/TiO2 catalysts was strongly affected by the Re content, while the activity of Pt-Re/TiO2 catalysts was less dependent on the addition ratio of Re, and more dependent on the temperature of reduction. The formation of certain bimetallic clusters between Pt and Re or Pd and Re was confirmed in the cases of Pt-Re(2:3) and Pd-Re(1:1)/TiO2 catalysts; however a different addition manner was suggested for the later acceleration effect over Pd-Re(1:10)/TiO2 catalysts. The FT-IR analyses of the adsorbed species during the reaction exhibited the enhancement of the adsorbed CO peaks in lower wavenumber region with the increase of Re content. Accordingly, Re is supposed to have some effect on these adsorbed CO, which accelerates the WGS reaction, especially in the case of Pd-Re/TiO2 catalysts. (c) 2005 Elsevier B.V. All rights reserved.