A direct comparison x-ray method using crystal structure Information has been developed for rapid quantitative analysis of the oxide phases present in oxidized steels. This procedure is similar to that used for the analysis of retained austenite in hardened steels and requires no external or internal standards for accurate oxide determinations. Successful application of this technique has been achieved for a variety of steel oxide mixtures and excellent correlation with microstructural analysis results has been found. Accurate determinations have been made of the volume fractions of Wustite (FeO), Magnetite (Fe3O4) and Hematite (Fe2O3) for a wide range in steel carbon content and transformation treatments. Many oxide mixtures that differ over a wide range in the amounts of each of the three oxides phases have been measured successfully. The procedure is simple, the method direct and the analysis accurate.