Homoepitaxial strontium titanate (SrTiO3) thin films have been grown by pulsed laser deposition in order to identify those defects which are intrinsic to the growth of SrTiO3. The pulse rate and oxygen annealing pressure were varied, although the oxygen pressure bad no effect under these conditions. Columnar growth was common. The nature of the columns is described, but the reason for their presence is not fully understood. They can be suppressed using a high laser pulse rate. (c) 2006 Elsevier B.V. All rights reserved.