Thin films of Se80-xTe20Pbx (0 < x < 2) glassy semiconductors have been prepared by thermal evaporation of bulk material of the above composition prepared by melt quenching technique. The glass transition temperature "Tg", the peak crystallization temperature "Tp" and the melting temperature "Tm" of the bulk samples have been estimated from the Differential Scanning Calorimetry (DSC) data. The DSC studies were performed at a heating rate of 10 deg/min. It has been found that "Tg" initially decreases with small addition of Pb (x = 0.6), however its value increases with further addition of Pb (x > 0.6). This indicates that the addition of Pb (x >0.6) cross-links the already existing Se-Te chains, which in turn increases the chain length and results in the increase of Tg. The dc conductivity of the films has been measured as a function of temperature and is found to be activated in the entire temperature range. Its value increases from 10-9 to 10-5 (Ohm-m)-l with the addition of Pb to Se-Te system. The dc activation energy has been found to decrease from 0.67-0.23 eV with increase in Pb content. The optical energy gap determined at room temperature is found to decrease from 1.67-1.34eV with the addition of lead to the Se-Te matrix. The results are explained on the basis of enhanced valence band tailing when Pb is incorporated into the Se- Te system.