Abstract: A process for regenerating used catalysts having deposited on their surface contaminants comprising carbonaceous and/or sulfur-containing materials which comprises:a) contacting said particles in a fluidized bed with an oxygen-containing gas at an elevated temperature for a time which does not exceed about twenty minutes wherein at least about fifty percent by weight of the sulfur contaminants are removed, andb) passing the thus treated catalyst particles to a moving belt and causing the belt to move said catalyst particles through a furnace for at least about two hours, wherein said furnace is maintained at a temperature sufficient to remove the remaining portion of the contaminants from the particles.