Since the MgO-TiO2-Al2O3 system obeys interesting properties important for industrial applications: MgAl2O4-based materials have a good combination of physical and chemical properties such as high refractoriness, high mechanical strength and high resistance to chemical attack, while the addition of Al2TiO5 improves the thermal shock resistance of alumina-rich magnesium aluminate spinel. The binary MgO-Al2O3 [1] and TiO2-Al2O3 [2] systems were investigated experimentally and thermodynamic functions were re-assessed based on obtained results. However reported experimental data on phase equilibria in the MgO-TiO2 system are partially contradictory. There are three intermediate compounds in the MgO-TiO2 system. MgTi2O5 melts congruently at temperature of 1662-1690°C, whereas Mg2TiO4 and MgTiO3 melt by peritectic decomposition at 1740-1756°C and 1630-1680°C, respectively [3-5]. Also, two eutectics were reported: 1610-1630°C (~57.0 mol.% TiO2) and 1620-1632°C (75.0-80.0 mol.% TiO2). Earlier studies have proposed all intermediate compounds melt congruently [6]. Thus, the aim of present work is an experimental study of the phase equilibria in the MgO-TiO2 system to resolve contradictions between mentioned data as well as to define the low limit of thermal stability of Mg2TiO4. Samples containing 20.0, 33.3, 50.0, 56.0, 66.7, and 76.0 mol.% of TiO2 were prepared by co-precipitation, dried at 700°C for 1-2 hours, and then annealed for 1-18 days at temperature of 900-1400°C followed by air-quenching. By prolonged heat treatment at 900°C followed by XRD analysis mixture of MgTiO3 and MgO was stable instead of Mg2TiO4. This result is in agreement with calculations performed in [7] based on calorimetric data. Following results were obtained in the present work using DTA and SEM/EDX: MgTi2O5 melts congruently at 1667°C, and peritectic reactions with formation of Mg2TiO4 and MgTiO3 occur at 1767°C and 1636°C, respectively. Eutectics were detected at 1631°C and 1638°C (71.5 mol.% TiO2). Heat capacities of MgTiO3 and MgTi2O5 were measured in the temperature range between 200°C and 1100°C using DSC. The thermodynamic description of Pelton and Eriksson [8] was based on results [3-5, 7, 9, 10]. Results obtained in the present work and experimental thermodynamic data [9, 10] will be used to derive new thermodynamic description of the MgO-TiO2 system.