Mixed LaAlO3-SrTiO3 single crystals have been grown by using flame fusion, starting from homogeneously synthesized solid-solution powders. X-ray powder diffraction of the latter show the solid-solution system to be continuous over the whole composition range. Phase boundaries were determined by means of optical and calorimetric measurements. In the composition range of 100% to 20% LaAlO3, a cubic Pm3m to trigonal R3̄c phase boundary was observed. © 1983.