The selective, catalytic oxidation of CO in H-2-containing streams was investigated over titania-supported Co, Pt and Co/Pt catalysts. The work was motivated by the need to remove CO from the reformate fed to a polymer electrolyte fuel cell (PEFC) before it can poison the Pt anode. Pt/TiO2 catalysts were active over a broad range of temperatures With a maximum at 120degreesC. Co/TiO2 catalysts were effective for CO oxidation at high temperatures (>100degreesC). Mixed metal Co/Pt catalysts were quite effective, even at room temperature. The presence of H2O and CO2, major components of actual reformate, reduced the activity of all the catalysts tested, but less so for the Co/Pt catalyst. Activity decreased over long times but an intermittent, high-temperature "purge" regenerated the original activity. X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) were used to understand the synergism between metal components. The Pt either influenced activity by helping reduce the Co, or the Pt and/or Co stabilized a Ti suboxide state that may play a role in the reaction process. The latter is most likely attributable to the strong metal support interaction (SMSI) effect previously noted on Pt/TiO2 catalysts.