An experimental study of the constitution of the As&sngbnd;Te glasses has been carried out, using glass‐forming‐ability measurements, high‐angle diffraction, differential thermal analysis, and other thermodynamic determinations. Evidence is definitely given for a difference of valency between crystalline and glassy states. A model is suggested for the structural units in the glass and for the modifications induced by an excess of arsenic or tellurium with respect to the critical As2Te3composition.