In this work the structural and magneto-tran sport properties of the Sr2FeMoO6 double perovskite prepared using two elaboration processes are presented. The first process is the most used solid-state reaction technique starting from three materials: Fe2O3, SrCO3 and metallic MoO3 with the appropriate amounts. For this process, treatment conditions have been optimized in order to reduce the SrMoO4 amounts in the final compound. The best results have been obtained after annealing the mixture during 1 h at 700 degreesC under reducing 5% H-2-95% N-2 atmosphere followed by calcinations at 1200 degreesC under Ar atmosphere during 10 h. X-ray diffraction measurements have shown that the phase can be indexed within the 14/mmm space group indicating a tetragonal distortion. The magneto-tran sport measurements have shown the highest saturation magnetization value reaching 26.7 emu/g at 300 K and a magnetoresistance (MR) of 2.5%. For the second process, the phase has been elaborated using several steps and reacting at each step only two materials. In this case X-ray diffraction shows that the final compound is a single phase with the same space group as for the previous one. In contrast, the saturation magnetization is slightly smaller with 21 emu/g, while, at the opposite, the magnetoresistance is higher reaching 3.6%. These results will be discussed in correlation with the structural results. (C) 2004 Elsevier B.V. All rights reserved.