Greater knowledge of the interaction between soluble iron, dissolved organic carbon (DOC), and alternative oxidants is warranted if the latter are to be optimized for iron removal. An important conclusion of the work is that speciation of iron (differentiation of particulate, colloidal, and soluble forms) in source- and treated-water samples is needed to determine whether oxidant addition will prove advantageous. Source waters that contain predominantly particulate or colloidal iron may be effectively treated by coagulation and separation processes alone, whereas removal of soluble iron requires the addition of any one of the oxidants studied: potassium permanganate, chlorine dioxide, or hypochlorous acid. Both the concentration and nature of DOC in water were found to affect the residual iron speciation that followed oxidant addition. Includes 21 references, tables, figures.