This paper reports the magnetic, electrical, and microstructural properties of epitaxial thin films with an ordered double-perovskite structure. Sr/sub 2/ FeMoO/sub 6/ (SFMO) and Sr/sub 2/ CrReO/sub 6/ (SCRO) films have been grown by sputtering onto the lattice-matched substrates of Ba/sub 0.4/ Sr/sub 0.6/ TiO/sub 3/ -buffered and bare SrTiO/sub 3/, respectively. These films exhibit high saturation magnetization M/sub s/ values (3.8 /spl mu//sub B//f.u. for SFMO and 0.9 /spl mu//sub B//f.u. for SCRO), which are close to the expected values for their half-metallicity, and high curie temperature T/sub c/ values (385 K for SFMO and 620 K for SCRO). Surface analyzes by AFM and XPS indicate that these films have atomically flat and well-defined surfaces, which are free from any surface precipitates. This enables us to employ a standard photolithographic process for fabricating magnetic tunnel junctions based on these films. SFMO junctions with a native barrier formed by surface oxidation of a SFMO base-electrode and a Co counterelectrode have shown a tunnel magnetoresistance ratio of 10% at 4.2 K.