Recent breakthroughs in the preparation of transition metal oxide nanoparticles by solvent-deficient precipitation (SDP) provide exciting new possibilities for simpler and faster methods to prepare heterogeneous catalysts with small uniformly sized crystallites of the active phase. In this study, the authors apply the SDP method to prepare an unsupported iron FischerTropsch (FT) catalyst with a nominal composition of 100 Fe/5 Cu/4 K/16 SiO2 (relative mass) and an average crystallite size of 10-11 nm. Three preparations of this catalyst were made using SDP, and each was tested for over 200 h in a fixed-bed reactor to determine activity, selectivity, and stability. Values of the apparent first-order rate constants for syngas consumption at 260 degrees C were 215-251 mmol g(Fe)(-1) h(-1) MPa-1 for our catalyst compared to 155-265 mmol g(Fe)1 h1 MPa1 for literature catalysts not using a proprietary pretreatment (Bukur, D. B.; Lang, X. Ind. Eng. Chem. Res. 1999, 38, 3270-3275). Our catalyst was tested for more than 500 h and showed little or no downward trend with time, suggesting that the SDP method produces FT catalysts with not only high activity, competitive with the best reported in the literature, but also promising stability.