Garnet single crystals in solid solution were grown by the Czochralski method. Optical properties were estimated. In the transmission spectrum, small difference was observed between Dy3Ga5O12 and Dy3Al5O12. Shorter cut-off frequency on the transparency limit decreased with the decrease of the lattice parameter. New results which revealed that both refractive index and dielectric constant increased with the increase of their lattice parameters depending on an ionic radius of rare-earth ions were obtained. Garnet single crystals in solid solution hardened by the solid solution hardening. (C) 2002 Elsevier Science B.V. All rights reserved.