<p>Seven spent-catalyst samples from low-temperature Fe-based Fischer-Tropsch (FT) synthesis were investigated by Mössbauer spectroscopy at room temperature. The calcined precursor catalysts were prepared by three different methods: the historical Ruhrchemie method (3 samples), the organic-acid method (2 samples), and the goethite method (2 samples). The Mössbauer spectra were fitted, using Voigt-based line shapes, to two paramagnetic doublets and five magnetic sextets. The doublets are assigned to Fe²⁺ (larger quadrupole splitting) and Fe³⁺species, whereas the sextets are ascribed to the Hӓgg carbide (χ-Fe₅C₂) (fitted with three sextets having hyperfine magnetic fields of ~ 22, 18, and 10 T) and magnetite (Fe₃O₄) with its characteristic two-sextet pattern with hyperfine magnetic fields of ~ 48 T (A-site) and ~ 45 T (B-site). The Mössbauer relative areas, which give the relative proportions of Fe-containing phases, indicate that the catalyst samples prepared by the Ruhrchemie method contain large amounts of Fe-carbide (presumably the active phase in FT synthesis) compared to those prepared by the organic-acid and goethite methods. Furthermore, the Fe-carbide Mössbauer area is positively correlated with the calcined catalyst precursor surface area, which was found to positively correlate with the FT activity. The results indicated that the Ruhrchemie method is superior to the organic-acid and goethite methods for producing large proportions of Fe-carbide and thus high-performance low-temperature FT catalysts.</p>