Crude oils typically contain trace amounts of metals with vanadium and nickel being the most common. Usually they are in an oil-soluble form and in conventional refining processes they become concentrated in the residual fuel oil fractions. The deleterious effects of metals in petroleum have been known for some time. The metals not only contaminate the products, the metal chelates also cause poisoning and fouling of catalyst and corrode equipments. The metals also tend to form particulate emissions in the sub-micron range. This review presents discussion of methods for the removal of metals from the heavy oils and residuum fractions. These methods include physical, chemical and catalytic treatment processes. (C) 2006 Elsevier B.V. All rights reserved.