The phase equilibria in the Al2O3-SiO2-ZrO2 system up to a temperature of 2550.15 K, calculated using the Nuclea database, are considered in comparison with the experimental data available in the literature. The calculated eight isothermal sections of the phase diagram of the system under consideration are an addition to the previously obtained few experimental data. The phase equilibria in the Al2O3-SiO2-ZrO2 system are discussed in comparison with the corresponding binary systems.