Differential scanning calorimetry (DSC) data at different heating rates (5 less than or equal to alpha less than or equal to 50 K/min) of Ge20Te80 chalcogenide glass are reported and discussed. From the heating rate dependences of the glass transition temperature (T-g), the onset temperature (T-o) and the crystallization peak temperature (T-p), the activation energy for glass transition, E-g, and the activation energy for crystallization, E-c, were derived. The crystallization data are interpreted in terms of recent analyses developed for non-isothermal conditions. The obtained value of the Avrami index (n = 2.0 +/- 0.1) indicates that one crystallization mechanism, two-dimensional growth, is responsible for the amorphous-crystalline transformation. The calculated E-g and E-c are 134.1 +/- 3.5 and 184.3 +/- 3.5 kJ/mol, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.