Recent studies of the adsorptive and catalytic properties of magnetite (Fe//3O//4) are discussed with respect to the water-gas shift reaction (WGS) in this review article. Proposed mechanisms are examined, and the properties of the active sites required for these mechanisms are considered. Kinetic relaxation measurements of the rates of surface oxidation and reduction by WGS reactants and products suggest that a primary WGS pathway involves successive oxidation and reduction of the magnetite surface.