Calorimetric studies of amorphous Se75S25 Ag-x(x) (x = 2, 4, 6 and 8) chalcogenide glasses are made at different heating rates (5, 10, 15 and 20 K/min) under non isothermal condition using Differential scanning calorimetry. The values of glass transition temperature and crystallization temperature are observed to be composition and heating rate dependence. From the heating rate dependence of glass transition temperature and crystallization temperature, the activation energy for structural relaxation (Delta E-t), the activation energy of crystallization (Delta E-c) and the order parameter (n) have been calculated. It is observed that Se75S19Ag6 has a minimum value of activation energy for structural relaxation (Delta E-t), which indicates that this particular glass has a larger probability to jump to a state of lower configurational energy and higher stability in the glassy region. On the basis of the obtained experimental data the temperature difference (T-c - T-g) is found to be maximum for Se75S19AgG, which further indicate that this glass is the thermally most stable in the entire composition range of investigation. (C) 2008 Elsevier BY. All rights reserved.