Agx(Ge0.25Se0.75)100−x glasses with x varying from 0 to 25 have been shown to exhibit a conductivity threshold around x ~8–10. In this work, the structural changes induced by introduction of Ag in Ge25Se75 glass have been investigated using Raman and infra-red spectroscopies. In ambient conditions, changes are observed in position, width and intensity for vibrations assigned to Ge–Se bonds, showing that the tetrahedral network is relaxed and gains flexibility as Ag is introduced. High pressure experiments on two glasses containing 5 and 25 at.% Ag confirm that Ag-rich (25%) glasses clearly exhibit higher compressibility than Ag-poor (5%) glasses. Copyright © 2013 John Wiley & Sons, Ltd.