The influence of SO2, H2S and COS in low concentrations on the deactivation of PURh/BaO/Al2O3 NOx storage catalysts was investigated. Different samples of the catalyst were exposed to synthetic gas mixtures mimicking lean/rich engine cycling in a mixed lean application at 400degreesC. The lean gas mixture contained 8 vol.% O-2, 500 vol-ppm C3H6 and 400 vol-ppm NO balanced to 100 vol.% with Ar. The rich excursions were performed by switching off the oxygen supply. Sulphur, 25 vol-ppm of either SO2, H2S or COS, was added to the gas flow either during the lean, the rich or both periods. This procedure aimed at investigating the influence of the exposure conditions and therefore the lean and rich periods were kept equally long (5 min). In addition, thermodynamical calculations for the prevailing conditions were performed. It was concluded that all sulphur compounds investigated, i.e. SO2, H2S and COS, had similar, negative impact on the NO, storage ability of the catalyst and that they all showed increased deactivation rates during rich exposure compared to lean. During lean exposure, all sulphur carriers showed similar behaviour, while H2S and COS caused severe loss of noble metal activity during rich exposure.