A glass‐forming region in the As‐Te system extends from 42 to 52 at.% Te when conventional cooling rates are used. The glasses exhibited nonmemory and memory switching during ac pulsing, depending on the electrical treatment. X‐ray diffraction, DTA, and photomicroscopy were used to characterize structural changes occurring in glassy 48As‐52Te during conductance transition and switching. These data are interpreted to indicate that nonmemory switching in this bulk glass is caused by intermittent heating and cooling of a microvolume of glass during ac pulsing; memory switching is caused by the formation and melting of a crystalline As2Te3f