Single crystals of Sc2O3 hold great promise as potential hosts for high-energy lasers, but the extremely refractory nature of this oxide makes crystal growth difficult. Hydrothermal methods have been used to synthesize and grow single crystals of Sc2O3 and Er:Sc2O3 at a temperature over 1800 degrees C below their melting point. Scandia crystals up to 6 mm in size have been obtained by spontaneous nucleation. A preliminary hydrothermal growth study was performed and rates of up to 0.16 mm/day were observed for seeded growth of both Sc2O3 and Er:Sc2O3. Hydrothermal scandia has also been doped with trivalent Ho, Tin and Yb, making this an attractive technique for the growth of refractory optical crystals. (C) 2007 Published by Elsevier B.V.