The temperature dependence of CO-tolerant H-2 oxidation reaction (HOR) activity at Pt, Pt-Co, and Pt-Ru electrodes in 0.1 M HClO4 solution was examined with a channel flow electrode at 30 to 90 degrees C. The kinetically controlled current density ( j(K)) for the HOR at Pt decreased seriously at CO overage (theta(CO)) > 0.6 in the whole temperature range examined. In contrast, the Pt-Ru alloy exhibited an excellent CO tolerance: only 15% reduction in j(K) even at theta(CO) = 0.6 and 30 degrees C. The Pt-Co alloy also showed moderate CO tolerance up to 70 C. It was found for these alloys that the CO adsorption rate was much slower than that of Pt and the HOR sites were not so rigidly blocked by adsorbed CO due to its enhanced mobility, resulting from their modified electronic structure of surface Pt sites. The activation energies for the apparent rate constants for the HOR were as low as 3.0 and 5.3 kJ mol(-1) at Pt and Pt-Ru, respectively, indicating that the high-temperature operation increases CO-free HOR sites as well as enhancing the HOR kinetics.