Abstract Polycrystalline and amorphous thin films of AgGaS 2 were grown by flash evaporation for the first time. From a detailed investigation of the growthconditions it was possible to derive the first so-called structural phase diagram of a ternary chalcopyrite compound. In addition, the crystallization behaviour of amorphous films in a second heat treatment step was studied extensively. The crystal structures and chemical composition were analysed by X-ray diffraction, thermogravimetry and atomic absorption spectroscopy. The films were characterized by electrical and photo-electrical measurements.