Calorimetric studies have been performed on the Se $_{80-x}$ Te20 Pbx ( $0 \leq x\leq 1.4$ ) samples at different heating rates (5−20 °C/min). The glass transition temperature T g, the peak crystallization temperature T p, and the melting temperature T m are found to increase with increase in heating rate. The apparent activation energies for glass transition E t and for crystallization E c have been calculated from the heating rate dependence of T g and T p respectively. The effect of Pb addition to the Se-Te matrix on the mechanism of crystal growth has been investigated. The glass transition temperature T g and the peak crystallization temperature T p initially decrease with small addition of Pb (x = 0.6) but increases with further addition of Pb (x > 0.6). The thermal stability and glass-forming tendency have also been studied.