In connection with the trend toward the production of agglomerates of higher basicity for blast-furnace production, there has been increased interest in the physicochemical properties of calcium ferrites. The present article is devoted to the study of the reduction of calcium ferrites by hydrogen at 700-1000 degree C by means of a dynamic method. Five stages of the process are revealed. Intermediate products of reduction are determined using X-ray structural and petrographic analysis.