Kinetic studies have been carried out on the hydrogen reduction of pure α-Fe2O3 doped with foreign metal oxides employing a sensitive micro-gravimetric technique. The results show that the reduction of pure Fe2O3 proceeds by a consecutive two-step mechanism via Fe3O4, the overall rate being controlled by the topochemical reduction of Fe3O4 while that of doped oxides and hematite ore takes place by a different mechanism involving the mixed ferrite formed. In addition, the reduction of pure Fe2O3 is catalysed by metal additives in the presence of water vapour. This enhancement in reduction rate is attributed to a "hydrogen spill-over" effect. © 1982.