This scientific paper gives consideration to the information on the structure of the triple component system, in particular MgO-Al2O3-TiO2 that serves as a basis for the production of thermal resistance materials. The structure of such binary systems as MgO-Al2O3, Al2O3-TiO2, MgO-TiO2 was described and the data available for the MgO-Al2O3-TiO2 system were given. Thermodynamic data on all the system compounds were also presented and used for the computation of a change in the free Gibbs energy in the temperature range form 800 K to 1 900 K for the basic exchange reactions. It was established that the triangulation of the MgO-Al2O3-TiO2 system was changed in the three temperature intervals: in the temperature range lower than 1 537 K TiO2 existed as the polymorphous modification, i.e. anatase; in the temperature range from 1 537 K to 2 076 K TiO2 existed as a polymorphous modification in form of rutile and tialite was stable; and at the temperatures above 2 076 K the availability of stochiometric compound of Al4TiO8 was possible. In the temperature range lower than 1 537 K the two-phase equilibra of Al2O3-MgTi2O5, MgTi2O5-MgAl2O4, MgTiO3-MgAl2O4, and Mg2TiO4-MgAl2O4 were stable; in the temperature range from 1 537 K to 2 076 K the two-phase equilibria of MgTi2O5-Al2TiO5, MgTiO3-Al2TiO5, MgTiO3-Al2O3, MgTiO3-MgAl2O4, and Mg2TiO4-MgAl2O4 were stable, and above 2 076 K the MgTi2O5-Al2TiO5, MgTi2O5-Al4TiO8, Al4TiO8-MgTiO3, Al4TiO8-Mg2TiO4, Al4TiO8-MgO, and Al4TiO8-MgAl2O4 systems were stable.