The possible origins of sulfur impurities in FCC gasoline are reviewed and discussed. Their mechanism of formation during the FCC process as well as their mechanism of transformation on hydrotreating catalysts are also examined. The article focuses on the desulfurization of FCC gasoline by means of catalytic processes considering the fact that deep desulfurization must be achieved (in accordance with new regulations) while preserving octane rating of the fraction. The various parameters (presence of a promoter, nature and modification of the support, additives and poisons) which may influence the selectivity in hydrodesulfurization (HDS) versus olefin hydrogenation are also discussed. Existing and potential processes for the HDS of FCC gasoline with octane preservation are described. (C) 2004 Elsevier B.V. All rights reserved.