The thermal stability of a-Bi0.5Se99.5-xZnx (x = 0, 0.1, 0.2, 0.5 and 1) glasses has been determined by an isothermal method. In this method, crystallization behavior has been studied by annealing the samples at higher temperature (between the glass transition and crystallization temperature). The glass transition and crystallization temperature were measured using differential scanning calorimeter (Model-DSC plus, Rheometric Scientific Company, UK). Annealing at higher temperature leads to the creation of crystalline phase. The activation energy of crystallization (DeltaE(c)) and order parameter (n) are calculated by fitting the values of the extent of crystallization (alpha) in the Avrami's equation. The temperature dependence of d.c. conductivity has also been measured for the study of the conduction mechanism in the same samples. (C) 2003 Elsevier Science B.V. All rights reserved.