The electronic structure of the TiO2-SiO2 interface has been investigated using X-ray absorption spectroscopy (XAS). TiO2 overlayers have been grown on two substrates, amorphous SiO2 and highly oriented pyrolytic graphite (for comparison), by evaporation of Ti in an oxygen atmosphere at room temperature. The evaporation rate was low enough to allow a detailed study of the early stages of growth, i.e., the submonolayer regime (theta < 1). The Ti 2p XAS spectra of the TiO2 overlayers have been measured for different coverages. The spectra corresponding to the submonolayer regime show an unusual shape not reported up to now. A comparison with existing atomic multiplet calculations indicates a significant decrease of the crystal field (approximate to 0.7 eV) as compared with bulk TiO2 (approximate to 1.7 eV) due to strong electronic interactions at the interface. The presence of the SiO2 substrate and the covalent character of the Si-O bonds lowers the crystal field of the TiO2 overlayer at the interface. In contrast, the graphite substrate inhibits the total oxidation of the overlayer forming Ti2O3. XAS has proved to be a useful experimental tool for the study of the electronic structure of interfaces.