The DSC curves were measured for samples with low(9 and 18 mola) and high(36 and 45 molx) PbF, concentra- tion. From Dsc curves glass transition temperatures, Tr were evaluated. The inset of Fig. 1 shows variation of glass transition temperature with PbF2 content The value of T for sample without close to 437 c. It is in a good agreement with thermal data obtained glass in Pros-Bao-Alzo for similar phosphate Lazo,-Euzo, system 126l Moreover, it is clearly seen that the glass transition temperatures are reduced with increasing PbF2 concen- tration in glass composition. Previous thermal investigations indicate that the value of strongly depends on olF ratio in glass host uction of the oxide components to the fluoride host matrices induces an