Extended abstract from a plenary talk by Paul G. Tratnyek at the Theis Conference on Iron in Groundwater, 15-18 September 2000, Jackson Hole, WY, USA. This abstract represents the beginning of our transition from thinking of contaminant reduction by zerovalent iron (ZVI) as reaction directly with Fe(0) to a more complete conceptual model that emphasizes the role of iron oxides as mediators of electron transfer from Fe(0) to contaminants. The proceedings of this conference were never published. The abstract was downloadable from http://ese.ogi.edu/tratnyek and http://cgr.ese.ogi.edu/iron when those servers were active. The version provide here is identical to the original except that the headers and footers have been updated.