The development of efficient catalysts for the in situ elimination of tar produced in the gasification of biomass represents an important stage in the production of a clean hydrogen-rich gas suitable for use in fuel cells. With this in mind, the incorporation of iron, a readily available, low-cost, and non-toxic material, in calcined dolomite and its constituent compounds, CaO and MgO, was investigated. The Fe/CaO, Fe/ MgO, and Fe/dolomite systems were prepared using two impregnation techniques to generate the Fe2+ and Fe3+ species, which were then carefully characterized. Tar conversion tests in the presence of these prepared catalysts were carried out in a microreactor, using toluene as the tar model component. The catalysts were characterized before and after the reactor runs [using X-ray diffraction (XRD), temperature- programmed reduction (TPR), and Mössbauer spectroscopy] to better identify the catalytically active phases and the competitive interaction of iron with CaO, MgO, and calcined dolomite under reaction conditions