The results of a flow reactor study of the sulfur dioxide oxidation over a 1975 production Pt/Pd monolithic catalyst are described. The effects of catalyst temperature, space velocity, oxygen concentration, sulfur dioxide concentration, and feedgas composition have been studied. The sulfur dioxide oxidation is kinetically limited below approximately 475 °C and approaches thermodynamic equilibrium at higher temperatures. In the kinetically limited region and in the absence of reducing gases, sulfur dioxide conversion is relatively independent of oxygen concentration (~0.01-5% O2). When the reducing gases, carbon monoxide, propylene, or hydrogen, are present, they are oxidized more readily than sulfur dioxide and hence serve to inhibit its oxidation at oxygen concentrations of less than ~1.0%. There is a range of oxygen concentrations which gives high conversion of carbon monoxide and propylene simultaneously with low conversion of sulfur dioxide. Catalyst aging causes significant reductions in sulfur dioxide oxidation activity while still maintaining moderate to high carbon monoxide and propylene oxidation activities.