AbstractHigh-temperature oxidation of E110 (Zr-1%Nb) zirconium alloy in steam at Т = 1100°C to various degrees has been carried out. Based on the studies of morphology and microstructure of the oxide film and metal, as well as on review of previously published results, the mechanism of alloy oxidation has been proposed, which includes oxide thickening close to the oxide/metal interface, growth of the thickened areas and their conversion into nodules, growth of the nodules and crowning of the metal surface (white spots), clustering of nodules under the formed oxide, formation of a double (white on the surface) oxide film and delamination of the oxide upper layer.