Good-quality crystals of KBe2BO3F2 (KBBF) were grown with dimensions up to 12 x 10 x 6 mm(3) using the hydrothermal method. Their structure was determined by X-ray diffraction analysis, and the optical properties were studied using transmission spectroscopy. KBBF crystals grew in a favorable habit leading to an isometric morphology with well-developed rohmbohedral facets. They were cut and polished along the desired orientation for fabrication of optical devices, which could not be realized using the crystals grown by flux method. (c) 2006 Elsevier B.V. All rights reserved.