Chalcogenide glasses from the GeSe2-GeTe-PbTe system are synthesized. The temperatures of glass-transition, crystallization and melting are determined using differential thermal analysis. On the basis of the obtained values the glass forming ability KG of the glasses is determined by HrubyÂs criterion. The maximum value of KG is obtained for composition (GeSe2)60(GeTe)20(PbTe)20. The minimal volume of the micro-voids Vh and the energy for their formation Eh are calculated. The values ofVh and Eh vary within 0.0219 Â 0.0320 nm3 and 15.89 Â 17.31 kJ/mol, respectively. The influence of the composition on the investigated characteristics is analyzed.