MnOx-CeO2-Al2O3 mixed oxide catalyst, which is efficient for soot oxidation in NO + O-2 with T-50 = 437 degrees C, shows a poor resistance to sulfur dioxide with T-50 raised to 534 degrees C. The sulfated catalyst was treated in a reducing atmosphere (5% H-2/He) at different temperatures (500, 600, and 700 degrees C). The catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, infrared (IR) spectroscopy, thermogravimetric analysis (TGA), temperature-programmed decomposition (TPD) of sulfates, and temperature-programmed reduction (TPR) of hydrogen. The catalytic activities for soot and NO oxidation were evaluated using the temperature-programmed oxidation (TPO) process. The sulfates can be only partially removed by the reduction treatment at low temperatures, whereas the sintering of metal oxides turns to be a more important factor responsible for the deactivation of catalysts reduced at high temperatures. The optimized treatment temperature is 600 degrees C, at which the reduced catalyst has a T-50 value of 466 degrees C for soot oxidation.