Sol-gel barium titanate films on quartz substrates annealed at 450, 600, and 700°C were studied using spectral ellipsometry and spectrophotometry in the region of intrinsic absorption bands to determine the thicknesses of surface layers, films, and film–air and fi lm–substrate transition layers. Decreases of the band gap, porosity, and thickness of the films and increases of their refractive indices and absorption with increasing annealing temperature were established. Spectra of refractive indices and absorption of the films were interpolated by dispersion formulas for new amorphous materials.