Long emission wavelength scintillators are strongly required from the viewpoint of the practical use of silicon photodiode, which has higher resolution with lower cost compared with photo-multipllier. Among the various scintillator emission centers, we regard emission from Yb3+ charge-transitions state (CTS) as a candidate. In order to investigate proper hosts for Yb3+ CTS, the yttrium gallium garnet host and lutetium aluminum garnet host were studied. Transparent and crack-free heavily Yb-doped YGG, i.e. {Y1-xYbx}(3)[Ga](2)(Ga)(3)O-12 (Yb: YGG, x = 0.15, 0.5, 1.0) and heavily Yb-doped LuAG, i.e. {Lu1-xYbx}(3)[Al](2)(Al)(3)O-12 (Yb: LuAG, x = 0.15,0.5, 1.0) single crystals could be grown by the Modified Pulling Down method with < I I I > orientation. Emission, excitation spectra and decay kinetics were measured for these crystals. The CT transition of Yb3+ in the yttrium gallium garnet host was discussed compared with the Yb3+ one in the lutetium aluminum garnet host. (C) 2002 Elsevier Science B.V. All rights reserved.