Thermal films on titanium surfaces were formed by heating titanium samples in air at atmospheric pressure. The optical constants, thickness. and structure of the formed films at various temperatures and times of heating were investigated by ellipsometry and Raman spectroscopy. The complex index of refraction and the thickness of generated films were determined by comparing the experimental loci Delta and Psi obtained by ellipsometric measurements with theoretical computed Delta vs. Psi curves. It was found that the thickness inhomogeneity and porosity of formed films increase with increasing temperature and the duration of the thermal treatment. Beyond a certain critical temperature, the appearance of some Raman bands and changes in their intensities indicated that the film transformed from amorphous to microcrystalline and crystalline structure.