Twenty-six glassy compositions, belonging to the GexIn6Se94-x and GexIn12Se88-x families of the Ge-In-Se system, were prepared from high purity constiment elements. Differential Scanning Calorimetry (DSC) measurements were carried out on these glasses. The DSC thermograms were used to determine the glass transition temperatures (T g) for the compositions examined. TheT g-composition dependence of the GexIn6Se94-x family shows a minimum inT g at a value of the average coordination number, 〈r⦔, equal to 2.4. For both families of the glasses examined, theT g-〈r〉 dependence displays maxima at 〈r〉=2.75 and 〈r〉=2.83 for GexIn6Se94-x and GexIn12Se88-x families, respectively. These results are interpreted by using the Phillips model of rigidity percolation and Chemically Ordered Covalent Network (COCN) model.