Isothermal section of the Al2O3–TiO2–Nd2O3 phase diagram at 1400 °C is constructed for the first time. It is the part of systematic investigations of Al2O3–TiO2–Ln2O3 (Ln=lanthanides,Y) systems. The 1400°C was taken as the temperature, at which no liquid is expected in the system. Samples were prepared by a chemical method. Samples were annealed in air at 1400°С for 80 hours and cooled in the furnace. Phases in the samples were determined by XRD analysis. New phases and appreciable homogeneity regions based on components and binary compounds were not found. Isothermal section consists of seven narrow twophase and eight three-phase regions. Triangulation of the system is determined by the phase Nd 2 Ti 2 O 7 , which is in equilibrium with compounds Al 2 TiO 5 , NdAlO 3 and system components TiO 2 and Al 2 O 3 . Formation of phases Nd 4 Ti 9 O 24 , Nd 2 Ti 3 O 12 and Nd 2 TiO 5 in binary boundary system TiO 2 –Nd 2 O 3 causes the appearance of partially quasibinary sections Al 2 TiO 5 –Nd 4 Ti 9 O 24 , Al 2 TiO 5 –Nd 2 Ti 3 O 12 and NdAlO 3 –Nd 2 TiO 5 . The obtained results make a significant contribution to the understanding of interactions between the components in the system studied. The system includes binary compounds with high electro-optical, ferroelectric, piezoelectric, photocatalytic properties, mikrowave dielectric ceramic. In addition, in the system we expects the existence of new three-phase and two-phase eutectics, which can be obtained in the form of high-temperature structural materials by the directional solidification. This fact opens up the possibility to fi nd and establish the coordinates of new three-phase and two-phase eutectics for directional solidifi cation and to obtain new high-temperature structural materials in the Al 2 O 3 –TiO 2 –Nd 2 O 3 system.