Ag2S-Ag2Se chalcogenides have been synthesized by heating stoichiometric mixtures of elementary substances in vacuum sealed quartz vessels. Optical microscopy, scanning electron microscopy, X-ray powder diffraction with high-temperature experiments and X-ray single-crystal method were applied to study synthesized silver sulfoselenides. The synthesized silver sulfoselenides are homogeneous under optical and scanning electron microscope. At room temperature, two Ag2S1-xSex polymorphs - monoclinic and orthorhombic - coexist in the interval of 0.6 < x < 0.8. Compositional gap between two solid solutions is absent. At higher temperature, an intermediate monoclinic phase was observed in the range of Ag2S0.25Se0.75-Ag2S0.175Se0.825.