Abstract: A nitrogen oxide storage catalyst which contains at least one catalyst material and at least one nitrogen oxide storage component from the group of alkali and alkaline earth metals. The nitrogen oxide storage component, after completing catalyst preparation, is present as finely divided barium sulfate, strontium sulfate, a mixture or mixed crystals of the two sulfates, or as their complete or incomplete decomposition product with an average particle size of less than 1 &mgr;m. Barium sulfate and/or strontium sulfate act as feed materials for the active storage component in the storage catalyst according to the invention. As a result of the reductive exhaust gas compositions occurring under normal automobile driving conditions barium sulfate and strontium sulfate decompose to compounds which are able to store nitrogen oxides. This compensates for the loss of active storage components which occurs due to aging.