Kinetics of low-temperature CO oxidation was studied under atmospheric pressure at 383 K in the initial rates region over 1wt%Pt-1wt%CeOx supported on air-oxidized activated carbon (AC2). Feed concentrations of 1-5 mol% CO and 1-2.5 mol% O-2 with balance He were used for CO oxidation in the absence of hydrogen. A simple power-function rate expression was obtained with reaction orders of -0.24 in CO and 0.98 in O-2, and a plausible LHHW expression compatible with mechanisms reported in the literature was proposed. Feed concentrations of 5 mol% CO and 2.5 mol% O-2 were used for investigating the effect of the presence of CO2 or H-2 on CO oxidation rates by partially replacing inert He with 2-4 mol% CO2 or 10-60 mol% H-2.