The kinetics of the reduction of ferrous oxide with hydrogen in a steady state fluidized bed have been correlated with a rate equation based on a reaction controlled at the oxide-metal interface and on a differential material balance which assumes that a close approach to piston flow prevails. The correlation gives an enthalpy of activation of 29,500 b.t.u./lb. mole for the reaction, which is in good agreement with McKewan's reported value of 27,500 b.t.u./lb. mole. The relationships developed are used to predict the effect of the important independent variables on the over-all kinetics of the system.