Strontium titanate (SrTiO3), a well-established traditional perovskite substrate as well as a promising substrate crystal for the epitaxy of new advanced perovskite-type thin films, suffers from the unavailability in adequate quality for the latter. To improve the situation attempts have been made to grow SrTiO3 at moderate temperatures (< 1535 degrees C) well below the melting temperature and under low temperature gradients by the topseeded solution growth method. Based on very special modifications of the growth conditions, virtually mosaicity-free SrTiO3 single crystals in the 1-2 cm range were obtained. High crystalline quality was verified by defect selective etching, rocking curve measurements, energy dispersive Laue mappings and by synchrotron XRay diffraction topography. The production of virtually subgrain-and dislocation free substrate crystals is essential to considerably improve characteristics of SrTiO3 based SQUIDs, transistors or memory devices and to allow an in-depth analysis of intrinsic and extrinsic factors influencing the properties of epitaxially grown oxide heterostructures.