The role of the synthesis conditions on the cationic Fe/Mo ordering in Sr2FeMoO6 double perovskite is addressed. It is shown that this ordering can be controlled and varied systematically. The Fe/Mo ordering has a profound impact on the saturation magnetization of the material. Using the appropriate synthesis protocol a value of 3.7 μB has been obtained. Mössbauer analysis reveals the existence of two distinguishable Fe sites and a charge density at the Fem+ ions significantly larger than 3d5 suggesting a Fe contribution to the spin-down conduction band. The implications of these findings for the synthesis of Sr2FeMoO6 having optimal magnetoresistance response are discussed. © 2001 American Institute of Physics.