The kinetics of the reaction between CO and O-2 Over bimetallic Pt-Rh/Al2O3 catalysts was studied with a differential fixed bed flow reactor running under reducing conditions (CO/O-2 > 5). Temperature, CO and O-2 partial pressures were in the range 25-500 degreesC, 5 x 10(-3) to 9 x 10(-3) and 0.25 x 10(-3) to 2 x 10(-3) atm, respectively. Kinetic results have been interpreted in the light of various mechanisms proposed in the literature. The best agreement is obtained with a mechanism scheme involving a bimolecular reaction between adsorbed CO and adsorbed O-2 molecules as determining step. A rate expression has been derived as a function of adsorption equilibrium constants Of O-2 and CO, lambda (O) and lambda (CO), and of the rate constant of the limiting step k respectively. These parameters have been estimated at 215 degreesC, then the influence of temperature lambda (i) and k has been investigated. Finally, the effect of NO addition to the feed upon the reaction rate has been studied. It is shown that CO is adsorbed much more strongly than O-2 under our experimental conditions.