The structure and dielectric properties of (As 2 S 3 ) 100−x (SbSI) x glasses and their transformation during the heat treatment have been investigated. It has been determined that all glassy alloys have a microgeterogeneous structure. It has been shown that anomalies on the temperature dependences of dielectric permittivity ε and tg δ are connected with the transition of glasses into a polar state followed by their crystallization. The crystallization of glasses is accompanied by a sharp increase in dielectric parameters conditioned by the formation of nanocrystalline inclusions in the glassy matrix which have ferroelectric properties. The structure arising in (As 2 S 3 ) 100−x (SbSI) x (50 < x < 100) glass matrix during its crystallization corresponds to that of crystalline SbSI. The size of crystalline inclusions and dielectric permittivity value of ferroelectric glass-ceramic depend on the heat treatment conditions.