Epitaxial films of mixed (Nb,Ti)O-2 rutile have been grown on TiO2(100) rutile at 600 degrees C by molecular beam epitaxy. These films grow in a laminar fashion for Nb mole fractions up to similar to 0.10. In addition, reflection high-energy and low-energy electron diffraction, along with x-ray photoelectron diffraction and Rutherford backscattering reveal that the overlayers possess excellent long- and short-range structure order up to 10 at. %. However, strain-induced disorder becomes prevalent for higher Nb mole fractions, and the surfaces roughen and become defected accordingly. X-ray photoelectron diffraction and Rutherford backscattering reveal that Nb atoms substitutionally incorporate at cation sites in the rutile lattice for all Nb mole fractions investigated, leading to a mixed rutile NbxTi1-xO2 phase. Analysis of Nb 3d and Ti 2p core-level binding energies reveals that the oxidation state of both Ti and Nb is +4.