The possibility of calculating the thermodynamic properties of glasses and melts in the Cs₂O-B₂O₃-SiO₂ system formed by two glass-former oxides and one modifier oxide with the use of the vacancy variant of the generalized lattice theory of associated solutions is demonstrated. A comparison with the experimental thermodynamic functions determined earlier by high-temperature differential mass spectrometry and electromotive force method shows that the calculations performed within this approach lead to reliable thermodynamic functions. The thermodynamic properties and structural features (the relative numbers of bonds with due regard for the second coordination sphere) of glasses and melts in the Cs₂O-B ₂O₃-SiO₂ system are analyzed in terms of the generalized lattice theory of associated solutions.