Scanning tunnelling microscopy (STM) and scanning tunnelling spectroscopy (STS) were used to study the electronic structure of the reduced TiO2(1 1 0) surface. At the occupied part of the spectra some states at energies of about 1.1 and 0.6 eV below the Fermi level were found. At the unoccupied part of the spectra, the presence of a surface state at an energy of about 0.6 eV above the Fermi level was observed. Their presence has been ascribed to the appearance of Ti2O3 regions on the TiO2 (1 1 0) surface. High temperature spectroscopy measurements indicated smooth insulator-metal transition (I-M) caused by bands overlap in Ti2O3, which takes place at elevated temperatures. (C) 2003 Published by Elsevier B.V.