In this review some aspects are shown of the role of Mossbauer spectrometry in the understanding and the development of catalysts for the hydrogenation of CO, such as Fe/ZrO2 for the production of light olefins, Fe/SiO2 to study the formation of iron pentacarbonyl and Co/Al2 O3. Applying this Fischer-Tropsch process fuels of high purity, chemical feedstocks and special chemicals by leading a mixture of CO and H2 over an iron (cobalt) based catalyst are produced.