Amorphous Ge 2 Sb 2 Te 5 phase change material is considered as a prototype material for non-volatile memories due to the reversibility of the amorphous-to-crystalline transition on a nanosecond timescale. In this context, the kinetics of atomic self-diffusion has important bearings for the crystallization process and the switching behavior of phase change materials. It is thus important for applications as well as for the general understanding of the rapid and reversible switching behavior to understand atomic self-diffusion, especially in the amorphous phase. However, up to now, reliable data on the kinetics of atomic self-diffusion in amorphous phase change materials is almost non-existent. For this reason, Te tracer diffusion was measured using secondary ion mass spectroscopy and applying the highly enriched natural 122 Te isotope. For the first time, Te self-diffusion coefficients in amorphous Ge 2 Sb 2 Te 5 are experimentally measured and the activation energy of Te self-diffusion was determined as (1.43±0.08) eV.