Iron-magnesium hydrotalcite-like compounds with Mg/Fe ratios from 1 to 10 were synthesized by using an NH4OH/(NH4)(2)CO3 solution as the precipitation agent. TG-DTA results showed that the decomposition of the samples proceeds in two stages at temperatures around 505 and 640 K, corresponding to the sequential loss of interlayer water, and hydroxide and carbonate groups. After calcination at 673 K, these samples are transformed into Fe-Mg mixed oxides with high surface areas around 200 m(2)/g and mesopores around 15 nm in diameter. The results of temperature-programmed reduction and Mossbauer spectroscopy revealed that the reduction of the calcined Fe-Mg HTLC samples proceeds in two steps from Fe3+ to alpha-Fe through Fe2+. While the pure iron sample was completely reduced to alpha-Fe at 673 K, less than 60% of iron species in the calcined Fe-Mg HTLC samples were reduced to alpha-Fe at 773 K. The catalysts prepared from Fe-Mg HTLC exhibited lower CO conversion and much higher selectivity to CO2 as compared to the pure iron catalyst in the Fischer-Tropsch reaction.