We report an electric-field-induced directional mass movement of Ge2Sb2Te5 in bottleneck geometry. Under high-electric-stress circumstances (>10(6) A cm(-2)), a mass of Ge2Sb2Te5 tends to move toward the cathode (-) by the remaining mass depletion at the anode (+). The high electric stress induces an asymmetric compositional separation such that Sb is distributed toward the cathode (-) whereas Te is distributed toward the anode (+). Ionicity in Ge2Sb2Te5 at high temperature and high electric stress can be one of the origins of the asymmetric behavior. The electric-field-induced mass movement may provide insight on the device reliability of phase-change random access memory.