Red mud is a residue in the production of alumina by the Bayer process. It contains oxides of iron and titanium, and has been shown to be active in sulfided form as hydrogenation catalyst. The evolution of sulfided red mud activity and selectivity with reaction time was studied for the hydrogenation of a light fraction of an anthracene oil. Texture, morphology and composition of fresh red mud, and catalyst samples collected at different reaction times, were characterized by nitrogen adsorption, SEM and SEM-EDX. It was found that the catalyst looses surface area and superficial iron as the reaction proceeds. The decrease of catalytic activity can be explained by a combination of both phenomena.