Basic thermal parameters such as the glass transition and crystallization temperatures of bulk GexSb40-xSe60 (x = 15, 20, 25, 27, 32 and 35) glasses have been determined by differential thermal analysis. The observed peculiarity in the variation of the glass transition temperature with the heating rate increase in the narrow range of average coordination number Z = 2.65-2.67 has been related to structural and chemical transitions. It has been established that especially the compositions at x = 20, 25 and 27 do not crystallize by the applied non-isothermal regime. Identification of the corresponding crystalline phases for the rest samples has been specified. The apparent activation energy of crystallization has values of similar to174 kJ mol(-1). (C) 2003 Elsevier B.V All rights reserved.