Transient experiments were performed to study sulfur deactivation and regeneration of Pt/BaO/Al2O3 and Pt/SrO/Al2O3 NOx storage catalysts. It was found that the strontium-based catalysts are more easily regenerated than the barium-based catalysts and that a higher fraction of the NOx storage sites are regenerated when H2 is used in combination with CO2 compared to H2 only.