The optical properties of thin SiO2-TiO2 sol-gel composite films were investigated using exact optical models and the Forouhi-Bloomer model, (Phys. Rev. B34, 7018 ( 1986)), which describes the optical dispersion of amorphous dielectrics. Films deposited on glass and silicon substrates, were characterized by optical transmission and reflection measurements. Theoretical spectra have been generated and fitted to the experimental ones via standard regression analysis techniques. The ( five) adjustable Forouhi-Bloomer parameters describing the dispersion of the complex refractive index, as well as the film thickness were determined. The refractive index and absorption coefficient of the films were found to depend on the molar contents of the component oxides. (C) 2004 Kluwer Academic Publishers.