The defects in Cr2-xTixO3 (x=0, 0.2 and 0.3) were studied by a combination of X-ray diffraction, density and electrical conductivity measurements supported by atomistic simulation. The results are consistent with the Ti being dissolved as Ti4+ compensated by Cr vacancies which associate to form complex defects of lower energy. Ti doping gives n-type semiconductivity due to a small concentration of Ti3+ in equilibrium with the complexes. (c) 2005 Elsevier B.V. All rights reserved.