We have prepared 1-μm-thick epitaxial BaTiO3 thin films on GdScO3(110) using pulsed laser deposition. The structural perfection of the films was revealed by a rocking curve width of Δω=0.13° for the 002 BaTiO3 reflection and a Rutherford backscattering spectrometry/channeling minimum yield, χmin, of 0.5% measured for the Ba signal behind the surface peak. High-resolution transmission electron microscopy revealed an epitaxial relationship between BaTiO3 and GdScO3 and a sharp interface between the substrate and the film. The refractive index of the BaTiO3 film was no=2.329±0.002 and ne=2.307±0.002 at a wavelength of 632.8 nm and no=2.248±0.002 and ne=2.228±0.002 at a wavelength of 1523 nm. The optical losses were less than 2 dB/cm at a wavelength of 632.8 nm. © 2003 American Institute of Physics.