In order to study the influence of the support on high dispersion catalysts used for the CO hydrogenation reaction, two catalysts, Fe/SiO 2 and Fe/A 2O 3, were prepared by the dry impregnation method. Selective chemisorption of CO, volumetric oxidation, and Mössbauer spectroscopy were used to determine the Fe species present as well as the metallic crystal size, the degree of dispersion, and the reduction percentage. The presence of small Fen crystallites with high dispersion was determined in both catalysts. Reaction rates were measured in a differential reactor and significant differences, about one order of magnitude less for the Al 20 3 than for the SiO 2 supported catalysts, were found in the methane turnover frequencies. They are attributed to the interaction between the metal and the supports. The selectivity difference is also discussed in connection with distinct surface properties.