An oxidation catalyst is described for the exhaust gas purification of utility vehicles with diesel engines, which contains a substrate and a catalytically active coating of platinum, active aluminum oxide and aluminum-silicon mixed oxide. The two oxidic support materials, aluminum oxide and aluminum-silicon mixed oxide, are catalytically activated with platinum, the majority of platinum being present on the active aluminum oxide. The oxidation catalyst is distinguished by good NO oxidation rates together with a high poisoning resistance against sulfur compounds.