Chemical reduction has long dominated thinking about the mechanism of aqueous contaminant removal in the presence of metallic iron (e.g. Fe0/H2O systems). However, a large body of experimental evidence indicates that chemical reduction is not adequate to satisfactorily explain the efficiency of Fe0/H2O systems for several substances or classes of substances. By contrast, the alternative approach, that contaminants are fundamentally adsorbed and co-precipitated by iron corrosion products seems to provide a better explanation of observed efficiency. The new approach appears to not be fully understood. The present communication aims at clarifying this key issue. It seems that a paradigm shift is necessary for the further development of the technology using Fe0 for water treatment.