Process for preparing a mixed metal oxide powder, in which oxidizable starting materials are evaporated and oxidized, the reaction mixture is cooled after the reaction and the pulverulent solids are removed from gaseous substances, wherein as starting materials, at least one pulverulent metal and at least one metal compound, the metal and the metal component of the metal compound being different and the proportion of metal being at least 80% by weight based on the sum of metal and metal component from metal compound, together with one or more combustion gases, are fed to an evaporation zone of a reactor, where metal and metal compound are evaporated completely under nonoxidizing conditions, subsequently, the mixture flowing out of the evaporation zone is reacted in the oxidation zone of this reactor with a stream of a supplied oxygen-containing gas whose oxygen content is at least sufficient to oxidize the starting materials and combustion gases completely.