The results are presented of a study of the mechanism of formation, in the course of activation and oxidation of CO, of catalytically active Fe-Mn-Al oxide systems produced by modified alkoxy synthesis. Mossbauer spectroscopy and X-ray diffraction analysis established that the heat treatment of gel produces a complex oxide comprising a two-phase system consisting of particles of Al-0 and X-ray-amorphous spinel Al-2-(x+y)FexMnyO3. It was established that the initial stage of CO oxidation by air oxygen on the catalytic system is characterized by a development period during which heterogenization of the system continues with the formation of gamma-Fe2O3 and Mn2O3 clusters. The existence of ＇＇left-hand＇＇ hysteresis of the graph of CO conversion in oxidation by air oxygen has been found for the case of a Fe-Mn-Al oxide system. An examination has been made of a possible mechanism of oxidation, including the participation of terminal Fe=O and Mn=O bonds as active oxidation centres.