AgIn1-XGaXSe2 crystals were grown by a vertical gradient freeze method. All samples were shown to have a chalcopyrite structure and n-type conductivity by means of X-ray diffraction (XRD) and thermoprobe analysis, respectively. Electron probe microanalysis showed all crystals to be In-poor. Lattice constants a and e, calculated from the XRD were found to be proportional to X values in the Agln(1-X)Ga(X)Se(2) crystals, indicating that they obeyed Vegard's law. Free exciton (FE) emission lines were clearly observed by photo luminescence at 77 K, indicating high crystal purity. The FE peak energies were seen to show a nonlinear dependence on the composition X values in the AgIn1-XGaXSe2 crystals. (C) 2002 Elsevier Science B.V. All rights reserved.