Phase equilibria in the AgGaGeS4-AgGaGe3Se8 system were investigated using differential-thermal analysis and phase X-ray diffraction. A continuous solid solution series was discovered in the system, and the mechanism of the formation of these solid solutions was determined. Single crystals of the solid solutions were grown by the Bridgman-Stockbarger method. The crystals are of n- or p-type conductivity and their bandgap energy varies from 2.25 to 2.80 eV. (C) 2010 Elsevier B.V. All rights reserved.