This paper presents various methods to reduce concentrations of trace metals in refinery wastewater. The phrase “to reduce concentrations of trace metals” is used rather than “to remove trace metals,” because removal, or treatment, is just one method to reduce metals concentrations. The other method is source control, i.e., reducing the amount of metals transferred to the wastewater from their source. Both source control and treatment will be discussed. The sources of metals in refinery wastewater are presented, followed by methods for controlling these metals at their sources. Treatment technologies for removal of metals from wastewater are then discussed.